Remove the WA_PaintOnScreen widget attribute for vide widgets

This attribute doesn't quite do what it used to do in
Qt 4.x anymore, and will lead to Qt not painting the video
at all.

Change-Id: I2338815756cab82ae152058ff5a7b5f14e07001e
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

examples/videowidget/videowidget.cpp

@@ -52,7 +52,6 @@ VideoWidget::VideoWidget(QWidget *parent)
 {
     setAutoFillBackground(false);
     setAttribute(Qt::WA_NoSystemBackground, true);
-    setAttribute(Qt::WA_PaintOnScreen, true);
 
     QPalette palette = this->palette();
     palette.setColor(QPalette::Background, Qt::black);