R1:36d936fe8ae2

Remove an unused method in Audit for building comment actions

Summary: Ref T2393. This has been obsoleted by stacked actions and is no longer used.

Test Plan: Grepped for callsites, viwed commits.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2393

Differential Revision: https://secure.phabricator.com/D17249