Fix comment box borders in timelines after Phriction commenting

Summary:
Ref T13202. In D19660, I added comments to Phriction and tweaked some CSS.

One of these tweaks was getting rid of an extra border which was rendering under the comment area. However, I took off too much and ended up removing borders from other applications.

I think we don't actually need this setNoBorder() stuff after all -- a later change was sufficient to stop the actual border I was trying to get rid of from rendering. So this mostly just reverts part of D19660.

This rendering still isn't perfect, but I'm fine leaving that for another day for now.

Test Plan:

• Viewed comment areas in Phriction. Saw correct number of borders (1).
• Viewed comment areas in Maniphest. Saw correct number of borders (1).
• Grepped for extraneous removed classs, no hits.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13202

Differential Revision: https://secure.phabricator.com/D19684