Fix mobile menus

Summary: The multiple icons are causing layout issues. This hides the unsused div (the real icon gets appended). We should probably clean this up next redesign.

Test Plan: test mobile layouts in Chrome, test main menu and application menu. Go to Differential, check those menus to.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9086