[Reminder] Remove entries properly

reminder/reminder.py

@@ -240,7 +240,7 @@ class Reminder(commands.Cog):
                 user = self.bot.get_user(user_id)
                 if user is None:
                     # Delete the reminder if the user doesn't have a mutual server anymore
-                    await self.config.remove(reminder)
+                    await self.config.user_from_id(user_id).clear()
                 else:
                     time_diff = datetime.datetime.fromtimestamp(reminder["end_time"]) - datetime.datetime.utcnow()
                     time = max(0.0, time_diff.total_seconds())