[Dark mode] disable patching for customPreviewComponent.css
[Dark mode] disable patching for customPreviewComponent.css

In https://crrev.com/c/2569767 I migrated the stylesheet but missed the
JS flag change.

TBR=aerotwist@chromium.org

Bug: 1152736
Change-Id: I0e9f4d44785855b8165154140192ee0d28b49b4a
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2575088
Reviewed-by: Jack Franklin <993fcadce4d04090da2fefd557a0995e7966c8d5@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