Remove ORDER_PATH_MODIFIED from Differential

Summary:
Ref T7803. This is a performance hack, not a real order, and isn't really meaningful or pageable.

After D12158, we constraint his query on `dateModified` anyway, which should generally give the database a relatively small result set to examine.

Test Plan: Browsed Differential and Diffusion. Checked query plan, it didn't look too crazy.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7803

Differential Revision: https://secure.phabricator.com/D12361

src/applications/diffusion/controller/DiffusionBrowseController.php

@@ -199,7 +199,7 @@ abstract class DiffusionBrowseController extends DiffusionController {
       ->withPath($repository->getID(), $path_id)
       ->withStatus(DifferentialRevisionQuery::STATUS_OPEN)
       ->withUpdatedEpochBetween($recent, null)
-      ->setOrder(DifferentialRevisionQuery::ORDER_PATH_MODIFIED)
+      ->setOrder(DifferentialRevisionQuery::ORDER_MODIFIED)
       ->setLimit(10)
       ->needRelationships(true)
       ->needFlags(true)