symmetrica: 2.0 -> 3.0.1

This switches to the sagemath fork, since the original upstream is no
longer maintained and sagemath has effectively maintained symmetrica
through patches for a while now. The update fixes one bug in particular
that has caused failures in the sagemath test suite:

https://github.com/NixOS/nixpkgs/issues/81449
https://trac.sagemath.org/ticket/15312
https://trac.sagemath.org/ticket/29061

Regarding the licensing change:

https://gitlab.com/sagemath/symmetrica/-/commit/7cf91b380078a4def28dd6bab2b4607e2346c650