Fix PhabricatorPolicyDataTestCase

Summary: Fixes T5219.

Test Plan: Ran `arc unit`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T5219

Differential Revision: https://secure.phabricator.com/D9326