Fixing tooltips not appearing in fullscreen editor

Summary: Ref T4714, fixing tooltips not appearing in editor when in fullscreen mode

Test Plan: Create paste, verify tooltips appear in comment text-editing bar, make comment box fullscreen, verify tooltips still appear.

Reviewers: chad, Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4714

Differential Revision: https://secure.phabricator.com/D8763