Rely on CommunityConfiguration's built-in audit log rather than adding our own.

Every edit to the opt-in set is recorded by CommunityConfiguration with the editing user, timestamp, and diff of the change; there is no need for M2 to reproduce this. A community reviewer asking "when was this opted in and by whom?" should be answerable from the existing audit trail, and documenting the pointer to that audit trail is a one-line deliverable in the M2 handover note to Product.