Allow deletion of protected branches docs

Issue has all the info needed.

• Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/21393
• MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11000

mentioned in issue #21393 (closed)

added repository label

added settings label

mentioned in commit f64dae78

mentioned in merge request !11536 (merged)

assigned to @axil

changed title from Allow deletion of protected branches to Allow deletion of protected branches docs

changed the description

changed milestone to %9.3

added docs-review and removed docs-missing labels

closed via merge request !11536 (merged)

mentioned in commit 378830c5

mentioned in merge request !14785