Merge branch 'remove-phabricator' into 'master'

Remove Phabricator task importer

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/119867



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Urvi Chetta <uchetta@gitlab.com>
Co-authored-by: Magdalena Frankiewicz <mfrankiewicz@gitlab.com>