Remove DataProcessor serialization workaround from VersionedDatasetBuilder

[kostaleonard]

Pending a fix to uqfoundation/dill#424, remove workaround provided by pulumi/pulumi#7755. Offending code reproduced below:

def _serialize_data_processor(self) -> bytes:
    """Returns the serialized representation of the data processor object.

    :return: The serialized representation of the data processor object.
    """
    # See below dill issue on by-value serialization of classes not in
    # __main__:
    # https://github.com/uqfoundation/dill/issues/424
    # The current workaround is provided here:
    # https://github.com/pulumi/pulumi/pull/7755
    obj_type = type(self.data_processor)
    obj_module = obj_type.__module__
    try:
        obj_type.__module__ = '__main__'
        return pickle.dumps(self.data_processor, recurse=True)
    finally:
        obj_type.__module__ = obj_module