Requeue backfilling epics to work items

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/153736



Merged-by: Alexandru Croitor <acroitor@gitlab.com>
Approved-by: Adam Hegyi <ahegyi@gitlab.com>
Reviewed-by: Alexandru Croitor <acroitor@gitlab.com>
Reviewed-by: Nicolas Dular <ndular@gitlab.com>
Co-authored-by: Nicolas Dular <ndular@gitlab.com>