Remove defunt project image choices

Summary: These are old project image choices, remove and only go with FontAwesome related images.

Test Plan: Project -> Edit Picture -> Save

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15051

scripts/celerity/generate_sprites.php

@@ -30,7 +30,6 @@ $sheets = array(
   'menu' => $generator->buildMenuSheet(),
   'tokens' => $generator->buildTokenSheet(),
   'login' => $generator->buildLoginSheet(),
-  'projects' => $generator->buildProjectsSheet(),
 );
 
 list($err) = exec_manual('optipng');