Apply correct line-height to diffs

The typography refresh exposes a small shortcoming in the CSS used
for diff display; there is no line-height applied, causing inconsistent
display between skin (ie. too high in Vector). Adding line-height to the
diffs corrects this.

Bug: 64653
Change-Id: I59dfe3e887c68a7034ef78f6873127ffe88b0cc1
Merge "Apply correct line-height to diffs"