Merge branch 'issue_454425' into 'master'

Finalize BackfillEpicIssuesIntoWorkItemParentLinks migration

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/157974



Merged-by: Adam Hegyi <ahegyi@gitlab.com>
Approved-by: Alexandru Croitor <acroitor@gitlab.com>
Approved-by: Adam Hegyi <ahegyi@gitlab.com>
Co-authored-by: Felipe Artur <felipefac@gmail.com>