remove append_from_srgb()

It's now no different than append(from_srgb).

Bug: skia:7419

Change-Id: I97c59b6987f033ec2f1859db40ca3056b87b370a
Reviewed-on: https://skia-review.googlesource.com/86741
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
18 files changed