[BEFORE RELEASE] Update json naming to whatever is decided in readability

Team hasn't concluded how to name json fields yet. ABC updater shouldn't be released until a convention is chosen. See issue:

https://github.com/abcxyz/readability/issues/28

This issue depends on an external decision from the readability repository (issue #28). First, check that issue to see if a naming convention has been decided. Then, locate the JSON field definitions in the abc-updater codebase and update them accordingly. The work is blocked until the upstream decision is made.

Rédigé par le modèle d'indexation à partir du texte de l'issue.