Turn off useLArFloat unconditionally in LArPileupTool
This should fix the MTPileup physics validation failure.
Previously this was turned on if we weren't doing bunch crossing by bunch crossing pileup or pileup overlay. As it turns out, the event at a time pileup mode isn't used any more in production so the LArFloat mode was never tested.
MT pileup does use the event at a time mode, so LArFloat was turned on, and it seems it actually just doesn't work any more full stop, which is why the MT pileup output seemed to have very little pileup activity. Turning LArFloat off unconditionally seems to fix this (see the plots in ATLASSIM-7235).
Ping @tlari .
Edited by Beojan Stanislaus