Update arbiter.pyi

`Arbiter.LISTENERS` is actually a list of `BaseSocket`. 

You can see this if you follow the calls from [`create_sockets` in Gunicorn](https://github.com/benoitc/gunicorn/blob/56b5ad87f8d72a674145c273ed8f547513c2b409/gunicorn/arbiter.py#L156). It's also correctly `BaseSocket` in the [Typeshed `sock.pyi` file](https://github.com/python/typeshed/blob/main/stubs/gunicorn/gunicorn/sock.pyi#L35).

Author: topher200

stubs/gunicorn/gunicorn/arbiter.pyi

@@ -5,6 +5,7 @@ from typing import ClassVar
 from gunicorn.app.base import BaseApplication
 from gunicorn.config import Config
 from gunicorn.glogging import Logger as GLogger
+from gunicorn.sock import BaseSocket
 from gunicorn.workers.base import Worker
 
 from ._types import _AddressType
@@ -14,7 +15,7 @@ class Arbiter:
     WORKER_BOOT_ERROR: ClassVar[int]
     APP_LOAD_ERROR: ClassVar[int]
     START_CTX: ClassVar[dict[int | str, str | list[str]]]
-    LISTENERS: ClassVar[list[socket.socket]]
+    LISTENERS: ClassVar[list[BaseSocket]]
     WORKERS: ClassVar[dict[int, Worker]]
     PIPE: ClassVar[list[int]]
     SIG_QUEUE: ClassVar[list[int]]