Fix typo in box-plane test.

Bug: skia:9698
Change-Id: I18d7c65b09c236ed0d23689c71af44e9a0414de8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/258572
Auto-Submit: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
1 file changed