OIT Example: Remove unused property


The Particles 3D example uses "showOnlyDemos", but this one doesn't

Pick-to: 6.12
Change-Id: I1e743ec91b84557c601ae8c44740f95cdec185e2
Reviewed-by: Antti Määttä <antti.maatta@qt.io>
commit5a1e13d4f2fa4e8802ec80d0382dc773aefac354
parent4a96304d094d3567aaaeca16a5c8d91fb422712e
authorSze Howe Koh <szehowe.koh@gmail.com>
committerSze Howe Koh <szehowe.koh@gmail.com>
commit timeTue, 20 Oct 2026 08:41:15 +0000