remove SkBitmapProcState::fInvKy

It's only used in asserts, and it's completely redundant with other
asserts based on fInvMatrix.

Change-Id: I150dc5b948e5703fff75bf857cabb173428b081f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/249818
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed