Probably being the most prominent document demonstrating the problem,
configuration.nix(5) describes various types in plural, e.g.
- ` Type: list of strings`
- ` Type: list of systemd options`
However, there are other cases where appending "s" to the inner type
effectively changes the type, e.g.
- ```
Type: list of string matching the pattern
[a-zA-Z0-9@%:_.\-]+[.](service|socket|device|mount|automount|swap|target|path|timer|scope|slice)s
```
This should've read "list of string[s]..." but instead changes the
regular expression.
Simply drop the best-effort plural in favour of correctness and
simplicity rather than adding more grammar related logic/trying to fix
this.