GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
Teor has asked for updates in https://github.com/torproject/torspec/pull/61, but this PR has already been merged.
I have created a new PR for his suggestions: https://github.com/torproject/torspec/pull/63
I don't believe you can add to a merged PR so that's why a new PR exists.