multiwindow: Use showNormal() instead of show() to ensure normal geometry

Change-Id: Ice607f536a620da5a70f2ba066f4983bb78c6288
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

tests/manual/qopenglwindow/multiwindow/main.cpp

@@ -187,7 +187,7 @@ int main(int argc, char **argv)
         QPoint position = availableGeometry.topLeft();
         position += QPoint(col * windowWidth, row * windowHeight);
         w->setFramePosition(position);
-        w->show();
+        w->showNormal();
     }
 
     int r = app.exec();