Fix format string in websocket example

* Original commit: espressif/esp-idf@5288a797ef

examples/protocols/websocket/example_test.py

@@ -82,7 +82,7 @@ class Websocket:
                     return
 
             except socket.error as err:
-                print("Unable to establish a websocket connection: {}, {}".format(err))
+                print("Unable to establish a websocket connection: {}".format(err))
                 raise
 
     def handshake(self, data):