Replace BaselineProtocol::sysSleep with QThread::msleep

Just waiting can be done by QThread::msleep and we can get rid of ifdefery.
As an additional bonus the change removes the one single occurrence of winrt
code.

Task-number: QTBUG-84434
Pick-to: 5.15
Change-Id: I2b75e20cec16abbd93064722943f8977c0267bee
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>