Multiple holders on separated lines are detected as one.

input.txt:
```
Copyright: 2000-2010, Domenico Andreoli
2010-2011, Ramakrishnan Muthukrishnan
2011, Alessandro Ghedini
```

`scancode -ce --json-pp - input.txt`

Current results:

```json
"holders": [
{
"value": "Domenico Andreoli Ramakrishnan Muthukrishnan Alessandro Ghedini",
"start_line": 1,
"end_line": 3
}
],
```

Expected results: we should instead return 3 holders entries:
```json
"holders": [
{
"value": "Domenico Andreoli",
"start_line": 1,
"end_line": 1
},
{
"value": "Ramakrishnan Muthukrishnan",
"start_line": 2,
"end_line": 2
},
{
"value": "Alessandro Ghedini",
"start_line": 3,
"end_line": 3
}
],
```

`ScanCode version 21.2.25`