Remove "needWidgetData" from Conpherence

Summary: We no longer have widgets, don't need these calls for simplicity.

Test Plan: Add a user to a room, remove a user from a room. Grep for needWidgetData

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16562