Add Type Annotation for LangChain LLMs

[20001LastOrder]

In a couple of places of the code, we have something like

sherpa/src/sherpa_ai/policies/react_sm_policy.py

Lines 64 to 65 in b68c7b2

	# Cannot use langchain's BaseLanguageModel due to they are using Pydantic v1
	llm: Any = None

Because the type annotation was not supported by Pydantic v2. Recently versions of LangChain resolved this problem. So we should add these type annotations.