Modernize decay with AmpGen to match removal of _v1/_v2 from model name

In Sim10 AmpGen models have been cleaned up to remove _v1/_v2 from the name (lhcb/Gauss!488 (merged), deployed in Gauss v54r0). This is also the case in the external repository we are migrating to (lhcb/Gauss!670 (merged)).

The decay files have to follow, and there is a branch of DecFiles tevans/lbampgen-modernize that contains the relevant changes to the DecFiles.

This was observed to do a Sim10 validation request for Charm failing, LHCBGAUSS-2310