Fix broken quiz after refactoring

What does this MR do?

Fixes the broken quiz after refactoring the quiz module from model to gateway. See MR !998 (merged).

How confident are you it won't break things if deployed?

Should be beta-tested

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))