Fix warnings for -no-feature-dockwidget

Change-Id: Id1f04f9ff6da9bec07068d4ebed15f8bd29105af
Reviewed-by: Stephan Binner <stephan.binner@basyskom.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/widgets/widgets/qmainwindowlayout.cpp

@@ -2432,6 +2432,9 @@ QLayoutItem *QMainWindowLayout::unplug(QWidget *widget, bool group)
     }
 #endif
 
+#if !QT_CONFIG(dockwidget) && !QT_CONFIG(tabbar)
+    Q_UNUSED(group);
+#endif
 
     layoutState.unplug(path ,&savedState);
     savedState.fitLayout();