Fixed link in docs

Fixed User Data Stream Binance API link

Author: anson-vandoren

binance/websockets.py

@@ -432,7 +432,7 @@ def start_multiplex_socket(self, streams, callback):
     def start_user_socket(self, callback):
         """Start a websocket for user data
 
-        https://www.binance.com/restapipub.html#user-wss-endpoint
+        https://github.com/binance-exchange/binance-official-api-docs/blob/master/user-data-stream.md
 
         :param callback: callback function to handle messages
         :type callback: function