win: use modern API

Zhao Yuhang

2023-12-22 adb46e1e151b73e56a7e0066a896b48b92a7230e

 src/widgets/widgetwindowagent.h

@@ -26,6 +26,7 @@
        QWidget *systemButton(SystemButton button) const;
        void setSystemButton(SystemButton button, QWidget *w);

        // Not implement, don't use now
#ifdef Q_OS_MAC
        QWidget *systemButtonArea() const;
        void setSystemButtonArea(QWidget *widget);