Removed made-up kSBGRA pixel config.

We made up this pixel config and don't actually use it ourselves so lets
kill it for simplicity.

Change-Id: I6ae1c78fe7ada336a2411d295e8836dfeecb2d5c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/223979
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
19 files changed