Remove autojoin on upgrade as it's being moved to maubot

reminder/bot.py

@@ -212,6 +212,6 @@ class ReminderBot(Plugin):
 
     @event.on(EventType.ROOM_TOMBSTONE)
     async def tombstone(self, evt: StateEvent) -> None:
+        if not evt.content.replacement_room:
+            return
         self.db.update_room_id(evt.room_id, evt.content.replacement_room)
-        _, server = self.client.parse_user_id(evt.sender)
-        await self.client.join_room(evt.content.replacement_room, servers=[server])