[shaders] Fix CSS on main page.
[shaders] Fix CSS on main page.

Remove border on the details, and make the background
the correct color.

Also bump the textbox 8px to the right.

Bug: skia:13230
Change-Id: Ifaf322699aaf5649a3557b6e67e5a92e9de87ca9
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/535398
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot