PwCalculation: Fix restart validation for nscf/bands

[mbercx]

The PwCalculation input validation checks that for nscf and bands calculations the restart_mode is not explicitly set to restart:

aiida-quantumespresso/src/aiida_quantumespresso/calculations/pw.py

Lines 160 to 171 in 5cae75f

	@staticmethod
	def validate_inputs_base(value, _):
	"""Validate the top level namespace."""
	parameters = value['parameters'].get_dict()
	calculation_type = parameters.get('CONTROL', {}).get('calculation', 'scf')
	# Check that the restart input parameters are set correctly
	if calculation_type in ('nscf', 'bands'):
	if parameters.get('ELECTRONS', {}).get('startingpot', 'file') != 'file':
	return f'`startingpot` should be set to `file` for a `{calculation_type}` calculation.'
	if parameters.get('CONTROL', {}).get('restart_mode', 'from_scratch') != 'from_scratch':
	warnings.warn(f'`restart_mode` should be set to `from_scratch` for a `{calculation_type}` calculation.')

However, setting restart_mode to restart is a valid use case for interrupted nscf and bands runs (see #902 (comment)). So this validation should be removed.