Fix docs about ownership when QObject has a parent

If you return a QObject with parent from a Q_INVOKABLE it *does*
get QQmlEngine::JavaScriptOwnership. It just doesn't get deleted
by JavaScript (until you unset it's parent).

Change-Id: Id56debe06253ea1dd31dee844f5047d4ac055024
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/qml/doc/src/cppintegration/data.qdoc

@@ -52,8 +52,8 @@ remain with C++ by invoking QQmlEngine::setObjectOwnership() with
 QQmlEngine::CppOwnership specified.
 
 Additionally, the QML engine respects the normal QObject parent ownership
-semantics of Qt C++ objects, and will not ever take ownership of a QObject
-instance which already has a parent.
+semantics of Qt C++ objects, and will never delete a QObject instance which
+has a parent.
 
 
 \section1 Basic Qt Data Types