remove LEGACY_CONVEXITY code -- no more clients

Change-Id: Ifd33831b6a83a56685435ce8e4fbb218a147b34e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255981
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed