Allow the haunted comment panel ("Z") to take up more vertical room

Summary:
Ref T13151. See PHI685. When you haunt the panel, we only let it take up part of the screen. Let it take up slightly more of the screen so that it's more likely to fit completely on-screen without needing to scroll.

The behavior when it does scroll is fine (you get a scrollbar if your OS/browser is set up to show them) so this is a bit trivial/silly, but seems fine and doesn't have a big JS maintenance cost or anything.

Test Plan: Pressed "Z", resized my window to a weird tiny useless size, got slightly better (I guess) behavior.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13151

Differential Revision: https://secure.phabricator.com/D19480