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

scripts/celerity/generate_sprites.php

@@ -28,7 +28,6 @@ $generator = new CeleritySpriteGenerator();
 
 $sheets = array(
   'menu' => $generator->buildMenuSheet(),
-  'apps' => $generator->buildAppsSheet(),
   'apps-large' => $generator->buildAppsLargeSheet(),
   'tokens' => $generator->buildTokenSheet(),
   'gradient' => $generator->buildGradientSheet(),