Add G4NEUTRONXS data
In nightlies, lhcb-head slot Gauss using latest Geant4 fails due to missing G4NEUTRONXSDATA variable (and corresponding data). This MR should fix that by using latest version of NEUTRONXSDATA on CVMFS.
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In nightlies, lhcb-head slot Gauss using latest Geant4 fails due to missing G4NEUTRONXSDATA variable (and corresponding data). This MR should fix that by using latest version of NEUTRONXSDATA on CVMFS.