SkDocument: remove deprecated function

I meant to land this after https://crrev.com/2726103006 ,
but got sidetracked.

Change-Id: I4f0397302d41e89d2394bec545190cb024929bd8
Reviewed-on: https://skia-review.googlesource.com/17390
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
1 file changed