Stop OpenAI chat from emitting reference notes directly in chat body

The Chat models sometime output reference notes directly in the chat
body in unformatted form, specifically as Notes:\n['. Prevent that.
Reference notes are shown in clean, formatted form anyway

src/khoj/processor/conversation/openai/gpt.py

@@ -134,4 +134,5 @@ def converse(
         temperature=temperature,
         openai_api_key=api_key,
         completion_func=completion_func,
+        model_kwargs={"stop": ["Notes:\n["]},
     )