Quiz#max_score_cache is not updated after import from another quiz

@florian said:

🐛PROBLEME DE CALCUL DE POINTS muriel.bregou@orange.fr https://app.evalmee.com/courses#/22865/onlineexams/scores https://app.evalmee.com/courses#/22866/onlineexams/scores

probablement 2 versions dupliquées de https://app.evalmee.com/courses#/22767/online_exams/scores (qui lui n’a pas de problèmes)