This method is deprecated in Django 3.1[1], in favor of
django.urls.re_path(), and triggers the following warning.
RemovedInDjango40Warning: django.conf.urls.url() is deprecated in favor
of django.urls.re_path().
This was already fixed in Horizon by [2].
[1] https://docs.djangoproject.com/en/4.0/releases/3.1/#id2
[2] d9266fd82c1f0acc6b7236a6dc9b7e510985eb13
Change-Id: Iee805aa9b51f88756728be5df3aab8a196860a63