FYI: disabled "email" auth registration in phabricator

[Augie Fackler]

There's a TON of garbage unconfirmed accounts in phabricator, and to try and stem the tide I've turned off non-Google/BitBucket/Facebook account registration for now. Please feel encouraged to reach out if that's a problem for anyone.

(I feel like we should be able to require approval or something for new accounts but I don't see it, so this was a quick way to stop the bleeding.)