Fix two minor CSS states with Done button

Summary: Fixes T7737, gets rid of not-done hover yellow, and removed the pointer on button-done state for reviewer.

Test Plan: tested numerous states as reviewer and author. Rechecked done on a few items. Verify new states work. This still seems fragile.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7737

Differential Revision: https://secure.phabricator.com/D12313