Fix black background color of network preview pane
Fix black background color of network preview pane

It was mistakenly replaced by a theme color but in this case we explicitly want it to be always white.

I wonder if we should create `var(--color-white-always)` or similar to
allow for this.

Fixed: chromium:1185784
Change-Id: I1074c646f9956e21df161b73ad9c4654b14a02bb
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2763863
Auto-Submit: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>
Reviewed-by: Alex Rudenko <d8d88e7d7e77f69e23d1d1432231196fb8e02a62@chromium.org>
Commit-Queue: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend