Delete unused GrDebugMarkerOp.

Change-Id: Id3222effc21aea673b4d5d82a98e3e60f34512b1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/260278
Commit-Queue: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
13 files changed