R1:3f45defd3451

Clean up Remarkup Preview on mobile

Summary: Some space is bleeding in here from two-column-css. Re-scope CSS.

Test Plan: Review creating a task on mobile with document preview present.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D17712