text: Title: Fix warning: Directly instantiating an LLMMathChain with an llm is deprecated
  Body: It's reproducible by running `pytest`
  ```shell
  
  ======================================================== warnings summary ========================================================
  ../../pyenvs/langchain_api/lib/python3.9/site-packages/langchain/chains/llm_math/base.py:50
    /Users/alexander/pyenvs/langchain_api/lib/python3.9/site-packages/langchain/chains/llm_math/base.py:50: UserWarning: Directly instantiating an LLMMathChain with an llm is deprecated. Please instantiate with llm_chain argument or using the from_llm class method.
      warnings.warn(
  
  -- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
  ```
  
  