The default list of the MC associator (ChargedPP2MC) contains the
default Brunel output locations, like Rec/ProtoP/Charged, but the
PersistReco links will populate these locations with PersistReco
objects. Because we already explicitly add the unpacked PersistReco
locations to the associator's input list, there's no need for the
associator to also run over the Brunel locations.