Clarify ownership of scene in QGraphicsView::setScene() docs.

Change-Id: I550a02bce0633884ee1ffe2321c6462a34194f89
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>

src/widgets/graphicsview/qgraphicsview.cpp

@@ -1597,6 +1597,8 @@ QGraphicsScene *QGraphicsView::scene() const
     When a scene is set on a view, the QGraphicsScene::changed() signal
     is automatically connected to this view's updateScene() slot, and the
     view's scroll bars are adjusted to fit the size of the scene.
+
+    The view does not take ownership of \a scene.
 */
 void QGraphicsView::setScene(QGraphicsScene *scene)
 {