Merge branch 'russell/improve-manual-deploy-docs' into 'master'

Include UI message for reference

See merge request gitlab-org/gitlab!77839

doc/ci/environments/index.md

@@ -166,7 +166,7 @@ deploy_prod:
 
 The `when: manual` action:
 
-- Exposes a play button for the job in the GitLab UI.
+- Exposes a play button for the job in the GitLab UI, with the text **Can be manually deployed to <environment>**.
 - Means the `deploy_prod` job is only triggered when the play button is clicked.
 
 You can find the play button in the pipelines, environments, deployments, and jobs views.