Fix hover color on logo.

Summary: Fix the hover color behind the logo.

Test Plan: Test iOS, Chrome, and Firefox. Hover over logo, get background. Open Home menu on mobile, see proper spacing. Check app menu in Config.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2440

Differential Revision: https://secure.phabricator.com/D4714