refactor: remove unused webhook handler for wallets

it was only used in lnpay, opennode and alby which all had it disabled anayways with a pretty old TODO, so i guess the feature is disabled for a y ear now and nobody used it, so i just removed it

lnbits/tasks.py

@@ -6,7 +6,6 @@ import uuid
 from http import HTTPStatus
 from typing import Dict, List, Optional
 
-from fastapi.exceptions import HTTPException
 from loguru import logger
 from py_vapid import Vapid
 from pywebpush import WebPushException, webpush
@@ -75,17 +74,6 @@ def register_invoice_listener(send_chan: asyncio.Queue, name: Optional[str] = No
     invoice_listeners[name] = send_chan
 
 
-async def webhook_handler():
-    """
-    Returns the webhook_handler for the selected wallet if present. Used by API.
-    """
-    WALLET = get_wallet_class()
-    handler = getattr(WALLET, "webhook_listener", None)
-    if handler:
-        return await handler()
-    raise HTTPException(status_code=HTTPStatus.NO_CONTENT)
-
-
 internal_invoice_queue: asyncio.Queue = asyncio.Queue(0)