Docs: isUserInitiated should be userInitiated

The documentation at http://doc.qt.io/qt-5/qml-qtwebengine-webenginenewviewrequest.html#isUserInitiated-prop lists the property to see if a new window is initiated by a user as "isUserInitiated", but the QML property is actually just "userInitiated".

I am not sure if this doc is meant to represent the C++ class, but it is still a bit confusing: I do not see any other doc for the QML properties of "request". At first I thought the property "isUserInitiated" was giving the wrong result until I realized it was just undefined and I needed to use userInitiated instead.