Cleanup QDBusVirtualObjectPrivate

The class doesn't exist and should not be forward declared nor declared
as private of QDBusVirtualObject

Change-Id: Icf3ca2b2be5ae0a8111785af485a0b6601002a25
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/dbus/qdbusvirtualobject.h

@@ -52,7 +52,6 @@ QT_BEGIN_NAMESPACE
 class QDBusMessage;
 class QDBusConnection;
 
-class QDBusVirtualObjectPrivate;
 class Q_DBUS_EXPORT QDBusVirtualObject : public QObject
 {
     Q_OBJECT
@@ -64,7 +63,6 @@ public:
     virtual bool handleMessage(const QDBusMessage &message, const QDBusConnection &connection) = 0;
 
 private:
-    Q_DECLARE_PRIVATE(QDBusVirtualObject)
     Q_DISABLE_COPY(QDBusVirtualObject)
 };