Update step to copy secrets to sidekiq nodes in ref architectures

To get this in line with the 10/25/50k architecture and considering
this is needed, updates the instructions for the 3k and 5k reference
architectures with separate Sidekiq nodes, to also copy the secrets
files from the application nodes to the Sidekiq nodes.

doc/administration/reference_architectures/3k_users.md

@@ -1582,8 +1582,8 @@ On each node perform the following:
    ```
 
 1. Save the `/etc/gitlab/gitlab-secrets.json` file from one of the two
-   application nodes and install it on the other application node and the
-   [Gitaly node](#configure-gitaly) and
+   application nodes and install it on the other application node, the
+   [Gitaly node](#configure-gitaly) and the [Sidekiq node](#configure-sidekiq) and
    [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure).
 
 1. Verify the GitLab services are running:

doc/administration/reference_architectures/5k_users.md

@@ -1581,8 +1581,8 @@ On each node perform the following:
    ```
 
 1. Save the `/etc/gitlab/gitlab-secrets.json` file from one of the two
-   application nodes and install it on the other application node and the
-   [Gitaly node](#configure-gitaly) and
+   application nodes and install it on the other application node, the
+   [Gitaly node](#configure-gitaly) and the [Sidekiq node](#configure-sidekiq) and
    [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure).
 
 1. Verify the GitLab services are running: