[Redesign] Fix Conpherence crumb border

Summary: Ref T8099, Adds a border to ConpherenceView, but not other Views. Removed some old styles.

Test Plan: Visit Conpherence Room, Thread, and Search.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13062