remove unused mutate() apis

Whether we should shrink at the end of mutate() turns out to be moot.

:)

Change-Id: Ic29df5734e3057f165f695b2d03f8e7eb0eeb4dd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/277299
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Herb Derby <herb@google.com>
2 files changed