Fix particles demo page

Was using an old (unnecessary) CK construct that no longer exists

Change-Id: Ib56795d5588586f6da07e0c90e36c3aee1fbbb18
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456645
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
1 file changed