Remove sk_ClipDistance.

This was unused and did not work on non-GLSL backends.

Change-Id: I6bd314d43cfefa64871b5c0e964b5ae52e494164
Bug: skia:10757
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/319778
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
18 files changed