Fix style regression for diff change descriptions.
Review Request #13057 — Created May 22, 2023 and submitted
The change descriptions for diffs use the same
the file listing in the diffs. Unfortunately, some of the styles for
that class were moved to the listing's parent container in order to
facilitate the new docking behavior, which caused the look of diff
change descriptions to regress.
This change copies over the few styles we need in order for this to look
Published some updated diffs and saw the "Diff" entry in the change
description box looked correct.