Merge branch '395545-fix-approver-alert-in-yaml' into 'master'

Fix error messages for policy editor's yaml mode

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/124100



Merged-by: Simon Knox <simon@gitlab.com>
Approved-by: Simon Knox <simon@gitlab.com>
Reviewed-by: Artur Fedorov <afedorov@gitlab.com>
Reviewed-by: Martin Čavoj <mcavoj@gitlab.com>
Co-authored-by: Martin Čavoj <mcavoj@gitlab.com>