Remove old Audit code "Action" transaction editing code

Summary:
Ref T2393. This code is no longer reachable (we never had an API for auditing in Diffusion) and unused. Clean it up before implementing new states/actions.

(Note that code for displaying these transactions still needs to stick around for a bit, we'll just never apply new ones from here on out. They've been replaced with modular transactions.)

Test Plan: Grepped for usage, commentd on / audited a commit.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2393

Differential Revision: https://secure.phabricator.com/D17250