remove unused Mode from GrBlurredEdgeFP

Only Mode::kGaussian is used, so fold that through.

Change-Id: Ic87f66c913e4e64c28dade2f65a9034b163af3ee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375941
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed