Remove old references to SampleApp

Docs-Preview: https://skia.org/?cl=135570
Change-Id: I330ffa964c2d90ca8d3cd844aabcd8616ccd0540
Reviewed-on: https://skia-review.googlesource.com/135570
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
7 files changed