Apply suggestions from code review

Co-authored-by: Christoph Zwerschke <c.zwerschke@dkfz-heidelberg.de>

src/metldata/builtin_transformations/infer_relations/model_transform.py

@@ -160,5 +160,5 @@ def add_inferred_relations(
         )
 
     model_dict = model.model_dump()
-    model_dict.update({"classes": {**model.classes, **updated_class_defs}})
+    model_dict["classes"].update(updated_class_defs)
     return SchemaPack.model_validate(model_dict)