🎨 use better dict update syntax

Author: zunda-arrow

pincer/core/gateway.py

@@ -181,7 +181,7 @@ def append_handlers(self, handlers: Dict[int, Handler]):
         """The Client that uses the handler can append their own methods. The gateway
         will run those methods when the specified opcode is received.
         """
-        self.__dispatch_handlers = handlers | self.__dispatch_handlers
+        self.__dispatch_handlers |= handlers
 
     def set_session_id(self, _id: str):
         """Session id is private for consistency"""