Remove spacing after timeline on diffs

Summary: I assume this box is always after timeline

Test Plan: test a diff or two

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8230

src/applications/differential/view/DifferentialRevisionUpdateHistoryView.php

@@ -222,6 +222,7 @@ final class DifferentialRevisionUpdateHistoryView extends AphrontView {
 
     return id(new PHUIObjectBoxView())
       ->setHeaderText(pht('Revision Update History'))
+      ->setFlush(true)
       ->appendChild($content);
   }