freecad: remove mpi dependency

According to upstream, "Med Fichier can require MPI".
We do not have Med Fichier, so we can remove mpi.
If this causes issues, it should be reverted. However,
FEM still works, so this is probably fine.

(cherry picked from commit 7138517)

Author: LordGrimmauld

pkgs/by-name/fr/freecad/package.nix

@@ -17,7 +17,6 @@
   libspnav,
   libXmu,
   medfile,
-  mpi,
   ninja,
   ode,
   opencascade-occt_7_6,
@@ -106,7 +105,6 @@ freecad-utils.makeCustomizable (
       libGLU
       libXmu
       medfile
-      mpi
       ode
       vtk
       xercesc