Remove legacy withStatus() method from RevisionQuery

Summary: Ref T2543. All callsites are now in terms of withStatuses().

Test Plan:

• Called differential.query and differential.find from Conduit API.
• Grepped through all withStatus() callsites.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18396