Update README.md, improving sort of environment variables by lexicographical order.

doc/ci/variables/README.md

@@ -284,6 +284,8 @@ export CI_PROJECT_PATH="gitlab-org/gitlab-foss"
 export CI_PROJECT_URL="https://example.com/gitlab-org/gitlab-foss"
 export CI_REGISTRY="registry.example.com"
 export CI_REGISTRY_IMAGE="registry.example.com/gitlab-org/gitlab-foss"
+export CI_REGISTRY_USER="gitlab-ci-token"
+export CI_REGISTRY_PASSWORD="longalfanumstring"
 export CI_RUNNER_ID="10"
 export CI_RUNNER_DESCRIPTION="my runner"
 export CI_RUNNER_TAGS="docker, linux"
@@ -295,10 +297,8 @@ export CI_SERVER_VERSION="8.9.0"
 export CI_SERVER_VERSION_MAJOR="8"
 export CI_SERVER_VERSION_MINOR="9"
 export CI_SERVER_VERSION_PATCH="0"
-export GITLAB_USER_ID="42"
 export GITLAB_USER_EMAIL="user@example.com"
-export CI_REGISTRY_USER="gitlab-ci-token"
-export CI_REGISTRY_PASSWORD="longalfanumstring"
+export GITLAB_USER_ID="42"
 ```
 
 ### `.gitlab-ci.yml` defined variables