Manually switch to use more recent CLHEP version
Addresses ATLINFR-4682.
The full solution will be an update of atlasexternals to use version CLHEP_2_4_1_3_atl04
, but in the meantime we can already manually ensure that this CLHEP version gets used, while other changes are still being made to atlasexternals.
Edited by Stefan Richter