fix: remove dead DataSpecificationIEC61360.value_id JSON deserialization code (#509)

Previously, the `DataSpecificationIEC61360.value_id` attribute was 
removed from the metamodel of the AAS. However, we forgot to remove part
of the deserialization, so we parsed and immediately discarded this
attribute.

This removes the code artefact.

Fixes #504

Author: zrgt

sdk/basyx/aas/adapter/json/json_deserialization.py

@@ -511,8 +511,6 @@ def _construct_data_specification_iec61360(cls, dct: Dict[str, object],
             ret.value_list = cls._construct_value_list(_get_ts(dct, 'valueList', dict))
         if 'value' in dct:
             ret.value = _get_ts(dct, 'value', str)
-        if 'valueId' in dct:
-            ret.value_id = cls._construct_reference(_get_ts(dct, 'valueId', dict))
         if 'levelType' in dct:
             for k, v in _get_ts(dct, 'levelType', dict).items():
                 if v: