Merge branch 'fix/manual-pipeline-ui-unable-to-load-predefined-variables' into 'master'

fix: Use short ref name as fallback in pipeline UI

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/184052



Merged-by: Briley Sandlin <bsandlin@gitlab.com>
Approved-by: Briley Sandlin <bsandlin@gitlab.com>
Co-authored-by: Anna Vovchenko <avovchenko@gitlab.com>