[graphite] Update two GMs that use local matrices

Graphite requires graphite images to be graphite-backed.

localmatrixshader_nested, in particular, is useful for ensuring
local matrices are handled correctly.

Bug: skia:12701
Change-Id: Idda51eff6db2bfff68d6b6ca54fc292987b5860c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/536037
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
3 files changed