Update the docs monthly release process

The versions dropdown raketask now changes to the release
branch automatically.

doc/development/documentation/site_architecture/release_process.md

@@ -121,11 +121,10 @@ versions (stable branches `X.Y` of the `gitlab-docs` project):
    pipelines succeed:
 
    NOTE: **Note:**
-   The `release-X-Y` branch needs to be present locally,
-   and you need to have switched to it, otherwise the Rake task will fail.
+   The `release-X-Y` branch needs to be present locally, otherwise the Rake
+   task will abort.
 
    ```shell
-   git checkout release-X-Y
    ./bin/rake release:dropdowns
    ```