Fix SKSL_ENABLE_TRACING flag in test code.

Change-Id: I2deb2be803a6154d4f75044ffc0f7338d8c5b94c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/795777
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Nolan Scobie <nscobie@google.com>
2 files changed