Remove unused methods from ConpherenceDurableColumnView

Summary: Calls to private methods ConpherenceDurableColumnView::buildStatusText() and ConpherenceDurableColumnView::buildSendButton() were removed in https://we.phorge.it/rP95d174956639aac7525d52368944edfff7cdb824

Test Plan: Grep the code; run static code analysis.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25784