Switch from GitLab staging to GitLab production URLs now all jobs
have been ported and tested to use GitLab instead of Phabricator.

If we land this right now, this would break some jobs that are triggered
on a regular basis (like swh-docs builds) as I also updated the git clone
URLs to the GitLab ones. So we should wait for GitLab production to be ready.

Depends on D9003