Remove detection of GL_ARB_fragment_coord_conventions

No longer used now that we create origin-neutral shaders and flip
with uniform values.

Bug: skia:12037
Change-Id: Ib63e6a3cc6fe625a671785f5cd592a0163f7bf64
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/426002
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
3 files changed