fix configuration errors of milvus

lightrag/kg/milvus_impl.py

@@ -32,8 +32,8 @@ class MilvusVectorDBStorage(BaseVectorStorage):
         )
 
     def __post_init__(self):
-        config = self.global_config.get("vector_db_storage_cls_kwargs", {})
-        cosine_threshold = config.get("cosine_better_than_threshold")
+        kwargs = self.global_config.get("vector_db_storage_cls_kwargs", {})
+        cosine_threshold = kwargs.get("cosine_better_than_threshold")
         if cosine_threshold is None:
             raise ValueError(
                 "cosine_better_than_threshold must be specified in vector_db_storage_cls_kwargs"