remove duet (source code unvailable) (#1010)

- ref: #1
- `https://duetapp.com/ : HTTPSConnectionPool(host='duetapp.com', port=443): Max retries exceeded with url: / (Caused by ConnectTimeoutError(<urllib3.connection.HTTPSConnection object at 0x7f5ae1b24d00>, 'Connection to duetapp.com timed out. (connect timeout=10)'))`
- https://github.com/awesome-selfhosted/awesome-selfhosted-data/actions/runs/12305999984/job/34346801761
- https://github.com/awesome-selfhosted/awesome-selfhosted-data/actions/runs/11902380190/job/33167270271
- Website with the Source Code and the Demo is down since over a month