sci-physics/geant-data: fix env for particle high precision data

sci-physics/geant-data: fix env for particle high precision data

As mentioned in [1], the variable G4PARTICLEHPDATA has been introduced
in Geant4 10.3 to be used as default base name for all particle data
modules. It substitutes G4PROTONHPDATA, G4NEUTRONHPDATA, etc. These
datasets are optional and have been included in Gentoo since Geant4 10.6
beta, but were using the old variable name.

1. https://cern.ch/geant4-data/ReleaseNotes/ReleaseNotes4.10.3.html#had-notes

Package-Manager: Portage-2.3.99, Repoman-2.3.22
Signed-off-by: Guilherme Amadio <amadio@gentoo.org>