Should use `fi_domain` and friends.

Geoff says:

>When Vampire outputs a traditional TPTP finite model it used to use the
fi_domain, fi_functors, and fi_predicates roles. In some recent times
the output has become non-TPTP-compliant, using the axiom role for
everything, e.g., ...
    https://tptp.org/cgi-bin/SeeTPTP?Category=Solutions&Domain=COM&File=COM014+1&System=Vampire-SAT---4.9.CSA-FMo.s

Oops, guess we broke it.