Configure reCAPTCHA score threshold for local development

[aduth]

🛠 Summary of changes

Adds a default score threshold for reCAPTCHA assessments in local development, to avoid having to require reviewers to specify this manually in application.yml in order to test related work (e.g. see Testing Plan in #10540).

📜 Testing Plan

1. Go to http://localhost:3000/
2. Create an account
3. When prompted to select MFA, choose phone
4. Enter an international phone number, e.g. +610491570006
5. In the reCAPTCHA score debugger tool, enter a value between 0.0 and 1.0
6. Click "Send code"
7. Observe that you are blocked if the score you entered was less than 0.5