Fix typo in docs.

No-Try: true
Docs-Preview: https://skia.org/?cl=146653
Bug: skia:
Change-Id: I1c0fb8bfb6f03291939215cceec603c578f68e63
Reviewed-on: https://skia-review.googlesource.com/146653
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
1 file changed