Remove obsolete dox w.r.t. filter-quality

Change-Id: Iab72a7e87445f821b887db32ee09a64700983077
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/345280
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed