Remove unused GM deferred canvas feature

Change-Id: I57b7fab34a46dd03a045800989e73f9001bdb6cb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/240506
Commit-Queue: Robert Phillips <robertphillips@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed