Update doc reference to PhabricatorIRCBot for D4757

Summary: Update doc reference to PhabricatorIRCBot for D4757

Test Plan: Read the docs

Reviewers: indiefan, epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11098