fix: sweagent prompt message SYSTEM_MESSAGE role set to user bug. (#1329)

Co-authored-by: aaren.xzh <aaren.xzh@antfin.com>

agenthub/SWE_agent/agent.py

@@ -75,7 +75,7 @@ class SWEAgent(Agent):
         )
 
         msgs = [
-            {'content': SYSTEM_MESSAGE, 'role': 'user'},
+            {'content': SYSTEM_MESSAGE, 'role': 'system'},
             {'content': prompt, 'role': 'user'}
         ]