Remove unused high-quality downgrade heuristic

Change-Id: I4c57f207497f6e701af517fe67c297e210c7ceae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/369997
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed