Remove hover state from labels in action list

Summary: This is wierd and I can't think of a use for it? Causing issues on hover states.

Test Plan: Action list, menus, dropdowns, etc. Labels shouldn't have hover states.

Reviewers: epriestley

Reviewed By: epriestley

Spies: Korvin

Differential Revision: https://secure.phabricator.com/D18463