Remove 1x AppIcons, use FontIcons instead

Summary: Removes the 1x application icons, and uses the fonticons instead. Feed was only known location.

Test Plan:
feed, dashboards, grep for use

{F275636}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: hach-que, Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11496

src/applications/diffusion/application/PhabricatorDiffusionApplication.php

@@ -19,7 +19,7 @@ final class PhabricatorDiffusionApplication extends PhabricatorApplication {
   }
 
   public function getFontIcon() {
-    return 'fa-code';
+    return 'fa-file-code-o';
   }
 
   public function isPinnedByDefault(PhabricatorUser $viewer) {