Its canonical source is now on GitHub and not in Wikimedia Git/Gerrit anymore, according to the extension maintainer in https://phabricator.wikimedia.org/T124640#1965199
(Filed this as a spin-off from T124978; following the instructions on https://www.mediawiki.org/wiki/Gerrit/Inactive_projects#Actions_to_deactivate_an_unused_repository )