[Reg 6.5 -> 6.8] QJSEngine garbage collector no longer frees unreferenced functions

#include <QCoreApplication>
#include <QJSEngine>
#include <QJSValue>
#include <QTimer>

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);
    QJSEngine engine;

    int counter = 0;

    QTimer timer;
    QObject::connect(&timer, &QTimer::timeout, qApp, [&]
    {
        engine.evaluate(QStringLiteral("let obj = { f: function() { return %1 } }").arg(counter));

        counter++;
        if (counter % 200 == 0) // Collect garbage every 2s
            engine.collectGarbage();
        else if (counter >= 1000) // Quit after 10s
            app.quit();
    });
    timer.start(10);

    return app.exec();
}