Remove userType() from public API for now

If added, will need to be through overloads, to not break source
compat. Will add them once there's a need.

examples/qtquick/customtitlebar/main.cpp

@@ -24,9 +24,8 @@ public:
 
     ~CustomFrameworkWidgetFactory() override;
 
-    QUrl titleBarFilename(int userType) const override
+    QUrl titleBarFilename() const override
     {
-        Q_UNUSED(userType);
         return QUrl("qrc:/MyTitleBar.qml");
     }
 };