Error validating Headscale postgres configuration

### Description

```
[config] ERROR:  - (0): database.postgres.pass must be a string (was missing) or database.type must be "sqlite" or "sqlite3" (was "postgres")
```

This error is false as the password is provided in an other field: `password_file`

### Headplane Version

nixos master

### Headscale Version

nixos master