Follow-up from "Improve review apps" -- parse JSON output rather than tab-separated

The following discussion from !6665 (merged) should be addressed:

• @rspeicher started a discussion: (+4 comments)

  Do the pipes explicitly need to be their own entry in the Array or can we just do command << %(| grep "#{release_name}"), for example? That said, %(| looks pretty weird too.

  This whole command looks a little daunting too, but I'm not sure how we can clean it up. 🤔

The other comments contain the actual details of what we want to do, but https://gitlab.com/gitlab-org/gitlab-ce/issues/49812. 😐