Remove unicode marks for "Accept/Raise Concern" in Audit

Summary:
Ref T13210. The comment action dropdown for audits has a heavy checkmark next to "Accept" and a heavy "X" next to "Raise Concern".

We previously removed similar marks in Differential in D19405 and that seems to have gone fine. For consistency, remove these too.

Test Plan: Viewed the comment action dropdown, no longer saw checkmark and X-mark.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13210

Differential Revision: https://secure.phabricator.com/D19759