Remove alpha modulation from more shader FPs

No longer necessary - incoming alpha is 1.

Bug: skia:11942
Change-Id: Idf94e9de95dd233a0559efec4ed50c79e3b2da2b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/469516
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
5 files changed