Make ManiphestAction extend from ManiphestConstants, not PhrictionConstants

Summary: See rPee620bde6dbc. Copy/paste derp. Not @vrana!

Test Plan: arc liberate

Reviewers: allenjohnashton, vrana, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D2604