Merge branch '442051-prevent-editing-synced-work-item-hierarchy' into 'master'

Prevent modifying hierarchy of a work item with synced epic

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/145507



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