T5015, Allow Herald rules for Maniphest to act on task status changes

Summary: Fixes T5015, Allow Herald rules for Maniphest to act on task status changes.

Test Plan: Create Herald rule for Maniphest tasks to flag a task with status "wontfix". Change status of Maniphest task to "wontfix". Task should be flagged.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T5015

Differential Revision: https://secure.phabricator.com/D10842