remove sksl interpreter guards

This is only used by particles, benchmarks, and tests,
and should be swept away by dead code elimination otherwise.

Change-Id: I10462d6ae0a08dd8219fc49325160ec6790632af
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/311759
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
9 files changed