remove open streaming platform (project archived)

- ref: awesome-selfhosted#1
- `https://openstreamingplatform.com : HTTPSConnectionPool(host='openstreamingplatform.com', port=443): Max retries exceeded with url: / (Caused by NameResolutionError("<urllib3.connection.HTTPSConnection object at 0x7facb29f63c0>: Failed to resolve 'openstreamingplatform.com' ([Errno -2] Name or service not known)"))`
- https://gitlab.com/osp-group/flask-nginx-rtmp-manager : archived

Author: Rabenherz112