db/disappearing_message: remove delete_all method

mautrix_signal/db/disappearing_message.py

@@ -58,10 +58,6 @@ class DisappearingMessage:
         q = "DELETE from disappearing_messages WHERE room_id=$1 AND mxid=$2"
         await cls.db.execute(q, room_id, event_id)
 
-    @classmethod
-    async def delete_all(cls, room_id: RoomID) -> None:
-        await cls.db.execute("DELETE FROM message WHERE room_id=$1", room_id)
-
     @classmethod
     def _from_row(cls, row: asyncpg.Record) -> "DisappearingMessage":
         return cls(**row)