Remove very old Audit status constants and AuditRequest data

Summary:
Ref T13631. See that task for discussion.

• "NONE": Probably never used?
• "CC": Obsoleted by subscribers.
• "AUDIT_NOT_REQUIRED": For Owners packages, obsoleted by edges.
• "CLOSED": For "Close Audit", obsoleted by "Request Verification".

Test Plan:

• Grepped for constants, browsed Diffusion.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13631

Differential Revision: https://secure.phabricator.com/D21598