fix RawMessagePollVoteEvent __slots__

Author: Readeem

discord/raw_models.py

@@ -817,7 +817,7 @@ class RawMessagePollVoteEvent(_RawReprMixin):
         The raw data sent by the `gateway <https://discord.com/developers/docs/topics/gateway#message-poll-vote-add>`
     """
 
-    __slots__ = ("user_id", "message_id", "channel_id", "guild_id", "data", "added")
+    __slots__ = ("user_id", "message_id", "answer_id", "channel_id", "guild_id", "data", "added")
 
     def __init__(self, data: MessagePollVoteEvent, added: bool) -> None:
         self.user_id: int = int(data["user_id"])