Make sure render json: ..., each_serializer: ... is working with Enumerables

If you try to render Enumerable with custom `each_serializer` then it will render with default serializer instead:

```ruby
render json: sequel_scope, each_serializer: CustomSerializer
```

This commit fixes this behaviour. Most likely fixes https://github.com/rails-api/active_model_serializers/issues/664 as well

test/fixtures/poro.rb

@@ -92,6 +92,10 @@ class ProfileSerializer < ActiveModel::Serializer
   attributes :name, :description
 end
 
+class DifferentProfileSerializer < ActiveModel::Serializer
+  attributes :name
+end
+
 class CategorySerializer < ActiveModel::Serializer
   attributes :name