Remove specific blend mode layout qualifiers

These were unused - we always enable the advanced blend equation
extension using "blend_support_all_equations" (if enabling the
extension is required at all).

Change-Id: I95fd6483ec54dfaf983290de95629fe0e86c22e8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/373877
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
12 files changed