freecad should depend on med not med-openmpi

med-openmpi requires h5py-openmpi which conflicts with python-h5py.

med-openmpi provides med, and freecad works with med, so freecad should depend on med rather than med-openmpi.

Ideally we should have an official "med" package (split from med-openmpi?).

I just tested this; built freecad with med-openmpi dependency moved to makedepends, uninstalled med-openmpi and export to a med file failed (missing .so file), then modified "med-openmpi" to "med" by removing " -D MEDFILE_USE_MPI=ON \" and freecad export to a .med file worked.