Add reCAPTCHA configuration overrides for Canada, Mexico

[aduth]

🛠 Summary of changes

Adds default reCAPTCHA score threshold configuration overrides for Canada and Mexico, so that they behave consistently across deployed environments.

📜 Testing Plan

Enable reCAPTCHA locally with configuration in config/application.yml:

phone_recaptcha_score_threshold: 0.5

1. Go to http://localhost:3000
2. Create an account
3. At MFA setup selection, choose phone
4. Enter a Canadian or Mexican phone number, e.g. 3065550100
5. In the "reCAPTCHA score" field (internal only), enter a number lower than the threshold defined in configuration, e.g. 0.4 if using the above-defined threshold
6. Submit the page
7. Observe that you pass successfully to the "Enter your one-time code" screen

[jmdembe]

Looks good to me