Change default UseMeasurementTracker to kNever in RectangularEtaPhiTrackingRegion

I think kNever is the only sensible default given that the default
argument for measurmentTracker is nullptr (was empty string).

HITrackingRegionForPrimaryVtxProducer and HITrackingRegionProducer
appear to use only the default value for this parameter since they do
not give measurementTracker argument (was measurmentTrackerName).