fix bookmaker

missed an example reference to SkTransferFunctionBehavior

TBR=caryclark@google.com
NOTRY=true

Docs-Preview: https://skia.org/?cl=142103
Bug: skia:6818
Change-Id: I966d37c0a2ad8154f81f801b3f523e899fcb9fde
Reviewed-on: https://skia-review.googlesource.com/142103
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
3 files changed