[xdoctest] reformat example code with google style in No. 214 (#56212)

python/paddle/distributed/fleet/base/private_helper_function.py

@@ -31,7 +31,7 @@ def wait_server_ready(endpoints):
     Examples:
         .. code-block:: python
 
-             wait_server_ready(["127.0.0.1:8080", "127.0.0.1:8081"])
+             >>> wait_server_ready(["127.0.0.1:8080", "127.0.0.1:8081"])
     """
     assert not isinstance(endpoints, str)
     while True: