Remove counts from home navigation

Summary: Ref T12136. This just yanks the band-aid off. Fundamentally these were useful well before Dashboards and advanced bucketing, but not so much any more. They also have some performance hit.

Test Plan: Add some tasks and diffs onto a new instance, see there is no count on the home menu bar.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12136

Differential Revision: https://secure.phabricator.com/D17238