Remove all "Phabricator Bot" code


Remove all "Phabricator Bot" code

Closes T7829 as wontfix. Closes T7965 as wontfix. Closes T7800 as wontfix. Closes T2731 as wontfix. Closes T1271 as wontfix.

We aren't maintaining this at all (see, e.g., T7829) and a user reported a technically accurate security issue via HackerOne: https://hackerone.com/reports/222870

Just throw it away until we get to the eventual Conphernece bot/API update and can do this stuff correctly.

Test Plan: Grepped for phabricatorbot.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7965, T7829, T7800, T2731, T1271

Differential Revision: https://secure.phabricator.com/D17756