Bugfix: Not all combine docs chains takes kwargs `prompt` (#3462)

Generalize ConversationalRetrievalChain.from_llm kwargs

---------

Co-authored-by: shubham.suneja <shubham.suneja>

langchain/chains/conversational_retrieval/base.py

@@ -172,15 +172,16 @@ class ConversationalRetrievalChain(BaseConversationalRetrievalChain):
         llm: BaseLanguageModel,
         retriever: BaseRetriever,
         condense_question_prompt: BasePromptTemplate = CONDENSE_QUESTION_PROMPT,
-        qa_prompt: Optional[BasePromptTemplate] = None,
         chain_type: str = "stuff",
+        combine_docs_chain_kwargs: Optional[Dict] = None,
         **kwargs: Any,
     ) -> BaseConversationalRetrievalChain:
         """Load chain from LLM."""
+        combine_docs_chain_kwargs = combine_docs_chain_kwargs or {}
         doc_chain = load_qa_chain(
             llm,
             chain_type=chain_type,
-            prompt=qa_prompt,
+            **combine_docs_chain_kwargs,
         )
         condense_question_chain = LLMChain(llm=llm, prompt=condense_question_prompt)
         return cls(
@@ -226,15 +227,16 @@ class ChatVectorDBChain(BaseConversationalRetrievalChain):
         llm: BaseLanguageModel,
         vectorstore: VectorStore,
         condense_question_prompt: BasePromptTemplate = CONDENSE_QUESTION_PROMPT,
-        qa_prompt: Optional[BasePromptTemplate] = None,
         chain_type: str = "stuff",
+        combine_docs_chain_kwargs: Optional[Dict] = None,
         **kwargs: Any,
     ) -> BaseConversationalRetrievalChain:
         """Load chain from LLM."""
+        combine_docs_chain_kwargs = combine_docs_chain_kwargs or {}
         doc_chain = load_qa_chain(
             llm,
             chain_type=chain_type,
-            prompt=qa_prompt,
+            **combine_docs_chain_kwargs,
         )
         condense_question_chain = LLMChain(llm=llm, prompt=condense_question_prompt)
         return cls(