fix unwanted title bar when special effect is enabled

Zhao Yuhang

2025-02-08 6f4ab6474fa81556b1d90f6f87f8322282d054db

 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);