update demo code

Zhao Yuhang

2024-09-15 f645ae48cda10b80ffe9d83ba9487671c7f535c0

 examples/mainwindow/mainwindow.h

@@ -30,8 +30,6 @@
protected:
    bool event(QEvent *event) override;

    void closeEvent(QCloseEvent *event) override;

private:
    void installWindowAgent();
    void loadStyleSheet(Theme theme);