fix Conpherence sorting

Summary: this broke when I moved sorting to the editor. Turns out you can't have custom hooks for the comment transaction, and thus I couldn't update participation inside the editor. This fixes this by removing the empty switch statement for the transaction type inside the parent class editor. This should have no effect other than fixing Conpherence. Note that conpherences will need another message, etc for a given conphernece to fix itself.

Test Plan: Conpherence threads were updated properly!

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2399

Differential Revision: https://secure.phabricator.com/D4817