Fix another typo in SkSize comments

Didn't notice that this was on both SkISize and SkSize the first time
around.

Change-Id: I20d7da0f653aeb4810ab67c9991646b16670497a
Reviewed-on: https://skia-review.googlesource.com/c/169889
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed