Remove old audit edit form in favor of Diffusion form

Summary: Since we embed comments/audits into Diffusion now, we don't need the
old edit interface.

Test Plan: Grepped for links to old interface.

Reviewers: btrahan, jungejason

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T904

Differential Revision: https://secure.phabricator.com/D1714