Tablet device_information manual test: show wheel events received

We have a bug that proximity events are generating them spuriously;
this is a way of testing it.

Task-number: QTBUG-52921
Change-Id: I490dfcf8d5b325f612b733e29fd49de9418bb19e
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>