fix(events): remove superfluous argument

[JamesDoingStuff]

Removes an argument that was temporarily used while testing #1386, fixing the following error:

2026-06-15 07:22:18,171 ERROR grpc._server - Exception iterating responses: _StompListener.__init__() takes 2 positional arguments but 3 were given
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/site-packages/grpc/_server.py", line 652, in _take_response_from_response_iterator
    return next(response_iterator), True
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/server/stomp-server.py", line 98, in StartEventSource
    conn_manager.create_connection(request)
  File "/server/stomp-server.py", line 53, in create_connection
    conn.set_listener("", _StompListener(self.queue, request.name))
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: _StompListener.__init__() takes 2 positional arguments but 3 were given