Fix post-GrFence removal comments.

Noticed some of these after submitting the removal CL.

Change-Id: I94b67fb1b76082b33a03e491bffb1d5eab934f4c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/803019
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
2 files changed