Update app.py

app.py

@@ -37,7 +37,7 @@ async def downdb():
     client = TelegramClient(None, api_id, api_hash)
     await client.start(bot_token=bot_token)
     os.remove('instance/database.db')
-    async for message in client.iter_messages(channel_username, limit=1):
+    async for message in client.iter_messages(channel, limit=1):
         await fast_download(client,message)
     
     return '2'