Fixes https://build.kde.org/view/Failing/job/Plasma/job/drkonqi/job/kf5-qt5%20WindowsMSVCQt5.14/

The fix still uses a deprecated method but it's the easier to put in place for now.
A clean fix would be:

QString str;
QTextStream ts(&str);
ts << Qt::hex << "0x" << qSetFieldWidth(8) << Qt::right << i;

and use str.
But as we are inside argument function, it would need a bit of rework.