Improve error message (#6275)

Trying to use OpenAI models like 'text-davinci-002' or
'text-davinci-003' the agent doesn't work and the message is 'Only
supported with OpenAI models.' The error message should be 'Only
supported with ChatOpenAI models.'

My Twitter handle is @alonsosilva
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Fixes # (issue)

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Co-authored-by: SILVA Alonso <alonso.silva@nokia-bell-labs.com>
Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

langchain/agents/openai_functions_agent/base.py

@@ -290,7 +290,7 @@ class OpenAIFunctionsAgent(BaseSingleActionAgent):
     ) -> BaseSingleActionAgent:
         """Construct an agent from an LLM and tools."""
         if not isinstance(llm, ChatOpenAI):
-            raise ValueError("Only supported with OpenAI models.")
+            raise ValueError("Only supported with ChatOpenAI models.")
         prompt = cls.create_prompt(
             extra_prompt_messages=extra_prompt_messages,
             system_message=system_message,