Add a `forget` command to remove a channel from monitoring

ahtcg_bot.py

@@ -34,6 +34,14 @@ class ArkhamDBUpdater(commands.Bot):
             with open('channel_list.json', 'w') as f:
                 json.dump(list(self.channel_list), f)
 
+        @self.command(name='forget')
+        async def forget(ctx: commands.Context):
+            """Remove this channel from the monitor list"""
+            await ctx.message.reply('No longer monitoring this channel for deck IDs', mention_author=True)
+            self.channel_list.discard(ctx.message.channel.id)
+            with open('channel_list.json', 'w') as f:
+                json.dump(list(self.channel_list), f)
+
     async def on_ready(self):
         print(f'Logged in as {self.user} (ID: {self.user.id})')
         print('Enabled on servers:')