[graphite] remove TEST_UTILS dep from sparse strips

Change-Id: Ia35c2497243b3cbdcff26ee875429ad3b350c710
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1278796
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
Commit-Queue: Thomas Smith <thomsmit@google.com>