lammps: remove deprecated MPIIO package not related to mpi

This lammps package was removed in this upstream commit:

https://github.com/lammps/lammps/commit/d230ae49c48a15ccefa6b3dcb091ecf508be4c52

MPI support is actually controlled by `BUILD_MPI` flag, documented in
<https://docs.lammps.org/Build_basics.html>. The next commit fixes that
for `lammps-mpi/package.nix`.

pkgs/by-name/la/lammps/package.nix

@@ -40,7 +40,6 @@
     SRD = true;
     REAXFF = true;
     PYTHON = true;
-    MPIIO = true;
   },
   # Extra cmakeFlags to add as "-D${attr}=${value}"
   extraCmakeFlags ? { },
@@ -75,9 +74,6 @@ stdenv.mkDerivation (finalAttrs: {
   ]
   ++ lib.optionals packages.PYTHON [
     python3
-  ]
-  ++ lib.optionals packages.MPIIO [
-    mpich
   ];
 
   passthru = {