remove unused code

Zhao Yuhang

2023-12-10 4085174ccca1f6c9490e333fdeea8e27041157ce

 examples/mainwindow/mainwindow.h

@@ -7,6 +7,9 @@
public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

protected:
    void installWindowAgent();
};

#endif // MAINWINDOW_H