net/mpich: upgrade to 4.1.2

Upgrade to 4.1.2

Release notes at https://www.mpich.org/2023/06/08/mpich-4-1-2-released/.

It also installs mpi_f08.mod and some other interfaces, but this requires
ISO_Fortran_binding.h to be found.

PR: 275317
Exp-run by: antoine@