remove GrTextBlob::setMinAndMaxScale from API

Change-Id: I7940fc31c7504e651cc1d035c662e4c1a403574e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/374358
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed