Remove calls to attachFilePHIDs in Conpherence Reply Handler

Summary: I missed removing this during the file purge of '16. Fixes T11717

Test Plan: Will test live

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T11717

Differential Revision: https://secure.phabricator.com/D16639