In previous refactoring, the CSS files are moved to subdirectory css

Change-Id: I38e05ae1a9e56f36d5bd25131e605a93cfdb61f9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3701958
Commit-Queue: Jie Pan <jie.pan@intel.com>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81120}