[REG 6.4.0 -> 6.4.1] Second ColorRole change via QPalette:setBrush() does not modify cacheKey

#include <QGuiApplication>
#include <QDebug>
#include <QPalette>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QPalette pal;

    qDebug() << pal.cacheKey();
    const QBrush red(Qt::red);
    pal.setBrush(QPalette::All, QPalette::ButtonText, red);
    qDebug() << pal.cacheKey();
    const QBrush green(Qt::green);
    pal.setBrush(QPalette::All, QPalette::ButtonText, green);
    qDebug() << pal.cacheKey();

    return 0;
}