rm SkRRectsGaussianEdgeMaskFilter

Neat but unused.

Change-Id: I1b2d160df274b05cfb5582a5385085cc2db89f7d
Reviewed-on: https://skia-review.googlesource.com/121960
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed