A case of nested Qt::WindowStaysOnTopHint may occur when
context menus are created on windows with Qt::WindowStaysOnTopHint
set. Raise the popup in that case.
Amends 329a029c36.
Task-number: QTBUG-62004
Change-Id: Ifb761edbd42b1447bec30735810c006d02e1aa97
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>