Remove unused SkCoverageModePriv code

Bug: chromium:1101491
Bug: b/161896447

The main goal is to replace "master" with more inclusive language.
Rather than updating the comment in this old, unused code, just delete
it.

Change-Id: I7fdc71ab8ee9ce7fc30bfb6929599d9ba05a82d1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306940
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Leon Scroggins <scroggo@google.com>
3 files changed