Upgraded django-recaptcha to 4.0.0.

[sarahboyce]

django-recaptcha 3.0.0 -> 4.0.0 to add Django 4.2 support
Migration guide: https://github.com/django-recaptcha/django-recaptcha/blob/main/CHANGELOG.md#400-2023-11-14

Impacted by renamed of captcha to django_recaptcha

Ref: #1437

[pauloxnet]

LGTM

[felixxm]

@sarahboyce Thanks 👍

[felixxm]

I had to revert this change because it blocked making donations. Recaptcha token was no longer available here:

djangoproject.com/djangoproject/static/js/mod/stripe-donation.js

Line 12 in 2b7c3bb

var recaptchaToken = document.getElementById('id_captcha').value;