Remove rhiwindow.qdoc example from 6.5 as this example was only
introduced in 6.6
Task-number: QTBUG-116068
Change-Id: Ia0bdc2122434adac51b37ba2207a2b0b993cf19b
(cherry picked from commit 3b187f14a1f80ac6893b5f7b5df9194691bc955c)
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
a3c1fb0567