Merge branch 'ph/465287/newMergeRequestBranchCheck' into 'master'

Fix new merge request branch validation check

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/155105



Merged-by: Kerri Miller <kerrizor@kerrizor.com>
Approved-by: Kerri Miller <kerrizor@kerrizor.com>
Co-authored-by: Phil Hughes <me@iamphill.com>