update the relay-guide HTTP redirect

The relay guide is now maintained on the community page and maintained by other people.

Please replace the redirect

torproject.org/relay-guide -> https://trac.torproject.org/projects/tor/wiki/TorRelayGuide

with:

torproject.org/relay-guide -> https://community.torproject.org/relay/

and remove 'nusenu' from the auto assigning Community/Relays trac tickets.