FIX: Load the category when the category_id attr is present. (PR #13621)

The store won’t autoload the reviewable category anymore as we removed that piece of code in #13412. This commit adds it as a computed property.


If #13412 was meant to remove unused code and it was actually used, why not just revert it?

I agree with @danielwaterworth - the revert is probably better

We’ll not revert the other commit as the topic also adds the category as a computed property.