Merge branch '27474-update-auto-deploy-requires-public-project' into 'master'

Resolve "Document that auto deploy only works for public projects"

Closes #27474

See merge request !8897

doc/ci/autodeploy/index.md

 # Auto deploy
-> [Introduced][mr-8135] in GitLab 8.15.
+> [Introduced][mr-8135] in GitLab 8.15. Currently requires a [Public project][project-settings].
 Auto deploy is an easy way to configure GitLab CI for the deployment of your
 application. GitLab Community maintains a list of `.gitlab-ci.yml`
@@ -33,6 +33,7 @@ enable [Kubernetes service][kubernetes-service].
 created automatically for you.
 [mr-8135]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8135
+[project-settings]: https://docs.gitlab.com/ce/public_access/public_access.html
 [project-services]: ../../project_services/project_services.md
 [auto-deploy-templates]: https://gitlab.com/gitlab-org/gitlab-ci-yml/tree/master/autodeploy
 [kubernetes-service]: ../../project_services/kubernetes.md