[graphite] Remove merge error comment from QueueManager

Leftover from I98d47739afeccd34d1b0913569677b68791cd89d

Change-Id: Ib3f90ad0b9d54521d525a0ea6360e59205ffd13c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/842502
Auto-Submit: Nolan Scobie <nscobie@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
1 file changed