This removes the following warnings.

```
activerecord/lib/active_record/relation/finder_methods.rb:252: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:258: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:268: warning: ambiguous first argument; put parentheses or a space even after `-' operator
activerecord/lib/active_record/relation/finder_methods.rb:274: warning: ambiguous first argument; put parentheses or a space even after `-' operator
```