Update Geant4 version to 10.6.3.13
Hopefully the final bump to the Geant4 external to resolve LTO-related warnings in Athena 24.0 builds!
Part of ATLASSIM-6058
Hopefully the final bump to the Geant4 external to resolve LTO-related warnings in Athena 24.0 builds!
Part of ATLASSIM-6058