Remove mentions of TBB 3.0
The transition phase to TBB 3.0 is over so i guess it is safe to remove them.
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.
The transition phase to TBB 3.0 is over so i guess it is safe to remove them.