This is no longer used anywhere.
```
$ grep -r "origin_add_one" $SWH_ENVIRONMENT_HOME/**/swh/*
swh-storage/swh/storage/cassandra/storage.py: self._cql_runner.origin_add_one(origin)
swh-storage/swh/storage/cassandra/cql.py: def origin_add_one(self, origin: Origin, *, statement) -> None:
swh-storage/swh/storage/in_memory.py: self.origin_add_one(origin)
swh-storage/swh/storage/in_memory.py: def origin_add_one(self, origin: Origin) -> str:
```
Note: those left are implementation details within the storage (it's no longer exposed through the storage interface)
Motivation:
- no longer used
- less to maintain
- no longer high number of logs about deprecated endpoints in console output
- and currently that means less to migrate to using data model objects
Related to T2494