Rename the _phabricator_time_format function for consistency
Summary: Ref T5655.
Test Plan: grep
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley, Blessed Reviewers
Subscribers: Korvin, epriestley
Maniphest Tasks: T5655
Differential Revision: https://secure.phabricator.com/D11187