remove (unused?) arcto patheffect

Bug: skia:
Change-Id: I80943cc495eb1edce839387f4b9512a66a4e5c11
Reviewed-on: https://skia-review.googlesource.com/25981
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
8 files changed