Removing Rails 6.0 deprecation warning
Removing Rails 6.0 deprecation warning

Prior to this change, specs reported the following warning:

```console
DEPRECATION WARNING: Delegating constraints to arel is deprecated and
will be removed in Rails 6.0.
```

I removed the deprecation warnings with this change (e.g. adding an
explicit call to #arel).

samvera/hyrax,samvera/hyrax,samvera/hyrax,samvera/hyrax