tweak IDPVM truthMinPt for ACTS ART 1 GeV muons
@astefl noticed that we were losing half the particles for the 1 GeV single muon samples. The reason was that, by default, IDPVM has a 1 GeV truth particle pT cut which was cutting half the delta function due to floating point precision. This MR recovers the missing particles in the 1 GeV single muon ACTS ART jobs, by reducing the pT cut to 0.999 GeV.
The physval_run4_mu1GeV_reco_r25.root Athena reference will need to be updated when this MR is accepted.