remove SkIPoint16 from documentation -- it is private

No-Try: true
Docs-Preview: https://skia.org/?cl=149267
Bug: skia:
Change-Id: Idee5487ceecd84c179f898afe3ebc63926608c56
Reviewed-on: https://skia-review.googlesource.com/149267
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
2 files changed