Remove extra workboard margin on mobile

Summary: We have too much space on workboards when displayed on mobile devices.

Test Plan: Shrink browser display, note that all workboards align to common gutters.

Reviewers: epriestley, btrahan

Reviewed By: btrahan

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8790

src/applications/project/controller/PhabricatorProjectBoardViewController.php

@@ -193,6 +193,7 @@ final class PhabricatorProjectBoardViewController
 
     $board_box = id(new PHUIBoxView())
       ->appendChild($board)
+      ->addClass('project-board-wrapper')
       ->addMargin(PHUI::MARGIN_LARGE);
 
     return $this->buildApplicationPage(