Improvement: Weaviate multitenant adddocs (#13827)

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- **Description:** Added a line to pass the tenant parameter to
add_data_object
  - **Issue:** An extra line added from the fix for #9956
  - **Dependencies:** n/a
  - **Tag maintainer:** @baskaryan 

Tested locally, works as expected with the line change.

---------

Co-authored-by: Simon Dai <simon6752@gmail.com>

libs/langchain/langchain/vectorstores/weaviate.py

@@ -164,6 +164,7 @@ class Weaviate(VectorStore):
                     class_name=self._index_name,
                     uuid=_id,
                     vector=embeddings[i] if embeddings else None,
+                    tenant=kwargs.get("tenant"),
                 )
                 ids.append(_id)
         return ids