settings_test.py:context_processors — remove implicit django.template.context_processors.csrf

The django.template.context_processors.csrf context_processor is added implicitly.

https://docs.djangoproject.com/en/3.2/ref/templates/api/#django.template.RequestContext https://docs.djangoproject.com/en/4.1/ref/templates/api/#django.template.RequestContext

Similar to hyperkitty!463 (merged)