Document that group Owners can always create subgroups
What does this MR do?
Adds missing docs that https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14046 introduced.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Adds missing docs that https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14046 introduced.