Fix default order for Differential queries
Summary:
Fixes T3781. The UI defaults to "Created" but the query defaults to "Modified". Make the two consistent.
In particular, an issue this fixes is that previously a /differential/?authors=duck page would show "Order: Created" but actually order by "Modified".
Test Plan: Visited /differential/?authors=duck and verified the revisions were ordered by creation date.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3781
Differential Revision: https://secure.phabricator.com/D6843