make SkRSXform singular

bookmaker complains that it doesn't know about SkRSXforms <- plural

Made them singular, made one 'SkRSXform array' since I think that
was the intent, don't know about the other one.

TBR=reed@google.com

Docs-Preview: https://skia.org/?cl=179730
Bug: skia:
Change-Id: I3d2194568a44e8e99995c0ff7b08b1f8b193abe7
Reviewed-on: https://skia-review.googlesource.com/c/179730
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
1 file changed