Chatbot example: clean up servers in correct order (#353)

examples/clients/simple-chatbot/mcp_simple_chatbot/main.py

@@ -284,12 +284,9 @@ class ChatSession:
 
     async def cleanup_servers(self) -> None:
         """Clean up all servers properly."""
-        cleanup_tasks = [
-            asyncio.create_task(server.cleanup()) for server in self.servers
-        ]
-        if cleanup_tasks:
+        for server in reversed(self.servers):
             try:
-                await asyncio.gather(*cleanup_tasks, return_exceptions=True)
+                await server.cleanup()
             except Exception as e:
                 logging.warning(f"Warning during final cleanup: {e}")