Drop Client::m_frameWrapper workaround for reparenting deco

No longer used, so we can just drop it.

Thanks to QtWayland for emitting a warning, which made me find this
useless code.

client.h

@@ -724,8 +724,6 @@ private:
     Xcb::Window m_client;
     Xcb::Window m_wrapper;
     Xcb::Window m_frame;
-    // wrapper around m_frame to use as a parent for the decoration
-    QScopedPointer<QWindow> m_frameWrapper;
     KDecoration2::Decoration *m_decoration;
     QPointer<Decoration::DecoratedClientImpl> m_decoratedClient;
     QElapsedTimer m_decorationDoubleClickTimer;

manage.cpp

@@ -706,7 +706,6 @@ void Client::embedClient(xcb_window_t w, xcb_visualid_t visualid, xcb_colormap_t
     xcb_create_window(conn, depth, frame, rootWindow(), 0, 0, 1, 1, 0,
                       XCB_WINDOW_CLASS_INPUT_OUTPUT, visualid, cw_mask, cw_values);
     m_frame.reset(frame);
-    m_frameWrapper.reset(QWindow::fromWinId(m_frame));
 
     setWindowHandles(m_client);