Remove unused kBufferSampler_GrSLType

Change-Id: I3e0476d92dfde928ef7d49155afdc3685c4ca03e
Reviewed-on: https://skia-review.googlesource.com/144023
Auto-Submit: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
5 files changed