Shorten text area in conpherence.

Summary: I'm having a hard time on a 15" display reading the thread due to the height of the text box. I shortened it and it still allows you to wax and wane for quite a while.

Test Plan: reload page, see shortened bar. Check FF and Chrome.

Reviewers: epriestley, btrahan

Reviewed By: btrahan

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4669