Add support for Django 4

[Toto Bille]

When updating to Django 4, the package is failing due to a Django deprecated dependency "ugettext":

```
  File ".../.venv/lib/python3.8/site-packages/django_openid_auth/admin.py", line 37, in <module>
    from django_openid_auth import views
  File ".../.venv/lib/python3.8/site-packages/django_openid_auth/views.py", line 52, in <module>
    from django_openid_auth.forms import OpenIDLoginForm
  File ".../.venv/lib/python3.8/site-packages/django_openid_auth/forms.py", line 36, in <module>
    from django.utils.translation import ugettext as _
ImportError: cannot import name 'ugettext' from 'django.utils.translation' (.../.venv/lib/python3.8/site-packages/django/utils/translation/__init__.py)
```

It seems there is a simple fix for this: https://stackoverflow.com/questions/57098515/python-with-django-import-error-with-registrationsupplementbase-cannot-import-na

I am unsure if there are others dependencies issues.

[youssri.ahmed (youssriaboelseod)]

replace "ugettext" by "gettext"