Ubuntu 24.04 + MPI

[jorgensd]

Currently, MPI4PY doesn't give the correct communicator with mpirun -n 4 python3 -c "from mpi4py import MPI; print(MPI.COMM_WORLD.size)".

Rolling back to ubuntu 22.04 it is restored.
Filed at: mpi4py/mpi4py#547 and will be reported to mpich to see if they know what's going on.