R1:b33bb3714bdb

Add some max-width to basic-nav

Summary: Fixes T12214. Adds a max-width

Test Plan: Tested on Home, Projects, Appsearch

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12214

Differential Revision: https://secure.phabricator.com/D17318