Date predicate is formatted as string

Hello,

in previous versions, block in this code use to receive a time object:

```
Ransack.configure do |config|
  config.add_predicate 'lteq_eod',
                       arel_predicate: 'lteq',
                       formatter: proc { |value| value.end_of_day },
                       type: :date
end
```

After upgrading from 4.3.0 to 4.4.0, the proc block started receiving an string.