Fix history_context handling error in kg_query

lightrag/operate.py

@@ -633,11 +633,8 @@ async def kg_query(
     # Process conversation history
     history_context = ""
     if query_param.conversation_history:
-        recent_history = query_param.conversation_history[
-            -query_param.history_window_size :
-        ]
-        history_context = "\n".join(
-            [f"{turn['role']}: {turn['content']}" for turn in recent_history]
+        history_context = get_conversation_turns(
+            query_param.conversation_history, query_param.history_turns
         )
 
     sys_prompt_temp = PROMPTS["rag_response"]