[canvaskit] remove POC Nima code

Now that drawVertices is exposed, no need to keep this around as a demo

Docs-Preview: https://skia.org/?cl=173994
Bug: skia:
Change-Id: I6293c8e2038ece27635d254db097e651c9d77a94
Reviewed-on: https://skia-review.googlesource.com/c/173994
Reviewed-by: Kevin Lubick <kjlubick@google.com>
5 files changed