Remove unnecessary return statement

Change-Id: If3e3e5c2cadf61a9296ef68525205cfcec6701e4
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/835277
Auto-Submit: Kevin Lubick <kjlubick@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>