Fix doc typo

NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=5942

Change-Id: I3861a4f56cd325b1bff322613d93c7b697492e75
Reviewed-on: https://skia-review.googlesource.com/5942
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Heather Miller <hcm@google.com>
1 file changed