BaseLammpsCalculation: Do not set CodeInfo.withmpi

The plugin was setting `CodeInfo.withmpi` based on the inputs from
`metadata.options.withmpi`. This is not necessary as the metadata option
is already handled by the `CalcJob` base class. The plugin implementation
should only set `CodeInfo.withmpi` if it wants to _force_ the code to be
run with MPI enabled or disabled.

The `CalcJob` base implementation used to not distinguish between the
two, but in aiidateam/aiida-core#5922 the
handling of MPI was improved. A `Code` can now define whether it
should be run with MPI or not and so the `CalcJob` class now has to
raise if the MPI setting of the code and the plugin clash. The `withmpi`
option, if explicitly set by the user, is also checked.

Since the plugin doesn't intend to enforce MPI or not, the setting on
the `CodeInfo` is removed.

aiida_lammps/calculations/lammps/__init__.py

@@ -372,7 +372,6 @@ def prepare_for_submission(self, tempfolder):  # pylint: disable=arguments-diffe
         codeinfo = CodeInfo()
         codeinfo.cmdline_params = list(self._cmdline_params)
         codeinfo.code_uuid = self.inputs.code.uuid
-        codeinfo.withmpi = self.metadata.options.withmpi
         codeinfo.stdout_name = self._stdout_name
 
         calcinfo = CalcInfo()

aiida_lammps/calculations/lammps/base.py

@@ -255,8 +255,6 @@ def prepare_for_submission(self, folder):
         codeinfo.code_uuid = self.inputs.code.uuid
         # Set the name of the stdout
         codeinfo.stdout_name = _output_filename
-        # Set whether or not one is running with MPI
-        codeinfo.withmpi = self.inputs.metadata.options.withmpi
 
         # Generate the datastructure for the calculation information
         calcinfo = datastructures.CalcInfo()