Merge branch 'prevent_type_convertion_for_synched_epic_wi' into 'master'

Reject conversion of Epic WIs that are a sync version of legacy Epic

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144615



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