Document Code Quality limitation
What does this MR do?
Document the limitation described in https://gitlab.com/gitlab-org/gitlab-ee/issues/2877 until a proper fix is introduced.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Document the limitation described in https://gitlab.com/gitlab-org/gitlab-ee/issues/2877 until a proper fix is introduced.