git: Redirect torspec.git gitolite to Gitlab

Greetings TPA team!

If you could setup the redirection from

https://gitweb.torproject.org/torspec.git -> https://gitlab.torproject.org/tpo/core/torspec

On our side, we will make the Gitlab repository the canonical one for torspec and thus push there by default form now on.

Note that at the moment, we push to gitolite and there is a hook pushing to Gitlab. This of course, is not needed anymore :).