Remove legacy picture-shader impl

Change-Id: Ibb4c49f101519b8290884f8da654b661e119de82
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/380916
Auto-Submit: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
5 files changed