zyBooks feedback is not showing

[apo5698]

Errors should be returned as the second element of the array:

# code above...
error = []
error << ["Total: #{actual} => #{point}"] if something_happen

[[point, '', 0], error]

https://github.com/apo5698/helli/blob/c291af6c22d3aeff284c3a807c010f5a7d27dabb/app/models/rubrics/item/zybooks.rb#L24-L26

Also change

https://github.com/apo5698/helli/blob/c291af6c22d3aeff284c3a807c010f5a7d27dabb/app/models/grade_item.rb#L101

to

self.error = capture[1]