Remove legacy matrix concat code

Chrome has been rebaselined to use the 4x4 concat

Change-Id: I36830a61ac2f2f44e0125798e8a7f12d79d9cbcb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290442
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed