Move Docker socket binding next to TLS/nonTLS alts

`Use Docker socket binding` is an alternative to [TLS
enabled](https://gitlab.com/gitlab-org/gitlab/-/blob/05ce22b8869cd308bcd259537eefd03ecf5f8f0e/doc/ci/docker/using_docker_build.md#L147)
and [TLS
disabled](https://gitlab.com/gitlab-org/gitlab/-/blob/05ce22b8869cd308bcd259537eefd03ecf5f8f0e/doc/ci/docker/using_docker_build.md#L244).
There is `Enable registry mirror for docker:dind service` in between
them which is unrelated.

doc/ci/docker/using_docker_build.md

@@ -363,6 +363,90 @@ build:
     - docker run my-docker-image /script/to/run/tests
 ```
 
+#### Use Docker socket binding
+
+The third approach is to bind-mount `/var/run/docker.sock` into the
+container so that Docker is available in the context of that image.
+
+NOTE: **Note:**
+If you bind the Docker socket [when using GitLab Runner 11.11 or
+newer](https://gitlab.com/gitlab-org/gitlab-runner/-/merge_requests/1261),
+you can no longer use `docker:19.03.12-dind` as a service because volume bindings
+are done to the services as well, making these incompatible.
+
+In order to do that, follow the steps:
+
+1. Install [GitLab Runner](https://docs.gitlab.com/runner/install/).
+1. Register GitLab Runner from the command line to use `docker` and share `/var/run/docker.sock`:
+
+   ```shell
+   sudo gitlab-runner register -n \
+     --url https://gitlab.com/ \
+     --registration-token REGISTRATION_TOKEN \
+     --executor docker \
+     --description "My Docker Runner" \
+     --docker-image "docker:19.03.12" \
+     --docker-volumes /var/run/docker.sock:/var/run/docker.sock
+   ```
+
+   The above command registers a new runner to use the special
+   `docker:19.03.12` image which is provided by Docker. **Notice that it's using
+   the Docker daemon of the runner itself, and any containers spawned by Docker
+   commands are siblings of the runner rather than children of the runner.**
+   This may have complications and limitations that are unsuitable for your workflow.
+
+   The above command creates a `config.toml` entry similar to this:
+
+   ```toml
+   [[runners]]
+     url = "https://gitlab.com/"
+     token = REGISTRATION_TOKEN
+     executor = "docker"
+     [runners.docker]
+       tls_verify = false
+       image = "docker:19.03.12"
+       privileged = false
+       disable_cache = false
+       volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
+     [runners.cache]
+       Insecure = false
+   ```
+
+1. You can now use `docker` in the build script (note that you don't need to
+   include the `docker:19.03.12-dind` service as when using the Docker in Docker
+   executor):
+
+   ```yaml
+   image: docker:19.03.12
+
+   before_script:
+     - docker info
+
+   build:
+     stage: build
+     script:
+       - docker build -t my-docker-image .
+       - docker run my-docker-image /script/to/run/tests
+   ```
+
+While the above method avoids using Docker in privileged mode, you should be
+aware of the following implications:
+
+- By sharing the Docker daemon, you are effectively disabling all
+  the security mechanisms of containers and exposing your host to privilege
+  escalation which can lead to container breakout. For example, if a project
+  ran `docker rm -f $(docker ps -a -q)` it would remove the GitLab Runner
+  containers.
+- Concurrent jobs may not work; if your tests
+  create containers with specific names, they may conflict with each other.
+- Sharing files and directories from the source repository into containers may not
+  work as expected since volume mounting is done in the context of the host
+  machine, not the build container. For example:
+
+   ```shell
+   docker run --rm -t -i -v $(pwd)/src:/home/app/src test-image:latest run_app_tests
+   ```
+
 #### Enable registry mirror for `docker:dind` service
 
 When the Docker daemon starts inside of the service container, it uses
@@ -505,90 +589,6 @@ The configuration is picked up by the `dind` service.
       sub_path = "daemon.json"
 ```
 
-#### Use Docker socket binding
-
-The third approach is to bind-mount `/var/run/docker.sock` into the
-container so that Docker is available in the context of that image.
-
-NOTE: **Note:**
-If you bind the Docker socket [when using GitLab Runner 11.11 or
-newer](https://gitlab.com/gitlab-org/gitlab-runner/-/merge_requests/1261),
-you can no longer use `docker:19.03.12-dind` as a service because volume bindings
-are done to the services as well, making these incompatible.
-
-In order to do that, follow the steps:
-
-1. Install [GitLab Runner](https://docs.gitlab.com/runner/install/).
-1. Register GitLab Runner from the command line to use `docker` and share `/var/run/docker.sock`:
-
-   ```shell
-   sudo gitlab-runner register -n \
-     --url https://gitlab.com/ \
-     --registration-token REGISTRATION_TOKEN \
-     --executor docker \
-     --description "My Docker Runner" \
-     --docker-image "docker:19.03.12" \
-     --docker-volumes /var/run/docker.sock:/var/run/docker.sock
-   ```
-
-   The above command registers a new runner to use the special
-   `docker:19.03.12` image which is provided by Docker. **Notice that it's using
-   the Docker daemon of the runner itself, and any containers spawned by Docker
-   commands are siblings of the runner rather than children of the runner.**
-   This may have complications and limitations that are unsuitable for your workflow.
-
-   The above command creates a `config.toml` entry similar to this:
-
-   ```toml
-   [[runners]]
-     url = "https://gitlab.com/"
-     token = REGISTRATION_TOKEN
-     executor = "docker"
-     [runners.docker]
-       tls_verify = false
-       image = "docker:19.03.12"
-       privileged = false
-       disable_cache = false
-       volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
-     [runners.cache]
-       Insecure = false
-   ```
-
-1. You can now use `docker` in the build script (note that you don't need to
-   include the `docker:19.03.12-dind` service as when using the Docker in Docker
-   executor):
-
-   ```yaml
-   image: docker:19.03.12
-
-   before_script:
-     - docker info
-
-   build:
-     stage: build
-     script:
-       - docker build -t my-docker-image .
-       - docker run my-docker-image /script/to/run/tests
-   ```
-
-While the above method avoids using Docker in privileged mode, you should be
-aware of the following implications:
-
-- By sharing the Docker daemon, you are effectively disabling all
-  the security mechanisms of containers and exposing your host to privilege
-  escalation which can lead to container breakout. For example, if a project
-  ran `docker rm -f $(docker ps -a -q)` it would remove the GitLab Runner
-  containers.
-- Concurrent jobs may not work; if your tests
-  create containers with specific names, they may conflict with each other.
-- Sharing files and directories from the source repository into containers may not
-  work as expected since volume mounting is done in the context of the host
-  machine, not the build container. For example:
-
-   ```shell
-   docker run --rm -t -i -v $(pwd)/src:/home/app/src test-image:latest run_app_tests
-   ```
-
 ## Making Docker-in-Docker builds faster with Docker layer caching
 
 When using Docker-in-Docker, Docker downloads all layers of your image every