Remove outdated color type readback workaround from dm

Change-Id: Ic3d9a17674baac8d567ee6229ee2ee0716d9dca9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289980
Auto-Submit: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed