[css-images-3] caniuse box makes both compat table and spec text unreadable

[litherum]

E.g. https://drafts.csswg.org/css-images-3/#repeating-gradients

[litherum]

cc @tabatkins @fantasai @LeaVerou

[tabatkins]

Oh, hrm, it's using the --bg-bordered-block color for its background, which is implemented as a mostly-transparent white in the darkmode colors (so you can more easily see it against any bg). That clearly isn't intended for things that can overlap, so I'll fix.

[tabatkins]

Okay, fixed on main, and I'll assemble a new pip release tomorrow.