Fix minimum_score for enterprise API

[basabin54]

Setting the minimum_score attribute to anything would cause the v3 check to fail automatically when using reCAPTCHA Enterprise because the score accessor was incorrect and would return nil every time. I simply corrected the accessor for the score attribute coming back from the API and it works again.

Pre-Merge Checklist

• [x] CHANGELOG.md updated with short summary

[grosser]

tests check for the old code ... please check the original code that added it for clues to why alternatively we could do score or fallback to this new code if you think that would work

[basabin54]

Sorry about that. I think it makes sense to fall back to the old accessor just in case. I've made that update

[grosser]

v5.12.2