Remove legacy canvas-matrix impl

Chrome (the only user of the flag) is now updated.

Change-Id: I137f471588238f2b1cd4bc6013affb8075d0c561
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263341
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed