We've had a long-standing issue where the Reviews and Diff tabs weren't

connected quite right to the review request box. They were fine on

Chrome and Safari, but would either appear to be connected with a solid

line or a fairly thin but visible line to the rest of the box on

Firefox.
This ended up being (at least on a high-DPI display) an issue with a

half-pixel height difference between these tabs and the rest of the

container. That came from the Star/Archive icons on the left-hand side

of the review request action bar, or, more specifically, their

line-height. We set that to inherit, but the default line height ended

up doing the wrong thing in our case.
We now set this explicitly to 0. This does not impact the display at

all, and it fixes the alignment issue.

Verified the display on Firefox. Also verified there weren't regressions

on Safari, Chrome, or Edge.