Remove Releeph "Authors" rules

Summary:
Fixes T3659. Releeph has some awkward complexity around who ends up as a commit author. Instead, we should always try to use the original author.

Metadata (like the requestor's identity) should be accessed via Conduit or other channels instead.

Test Plan: Saved some projects, grepped for all related symbols.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T3659

Differential Revision: https://secure.phabricator.com/D8630