Change HNL PIDs to 72, 74, 76
We change the HNL PIDs from 9900012, 9900014, 9900016 to 72, 74, 76 such that they get selected by MCutils as being exotic and appear in the TruthBSMWithDecayParticles container after the TRUTH3 derivation. We follow PDG-rule 11c) according to Zachs suggestion in an hn-atlas-PATHelp email discussion. Our current MC request can be found here: ATLMCPROD-10062.