Merge branch 'protected-branches-scb' into 'master'

Resolve CE/EE diffs in protected branches

Closes #11034

See merge request gitlab-org/gitlab-ee!12789

app/views/projects/protected_branches/_protected_branch.html.haml

 = render layout: 'projects/protected_branches/shared/protected_branch', locals: { protected_branch: protected_branch } do
-  = render partial: 'projects/protected_branches/ee/fallback_update_protected_branch', locals: { protected_branch: protected_branch }
+  = render_if_exists 'projects/protected_branches/update_protected_branch', protected_branch: protected_branch