[3.1.x] Fixed #31575 -- Added system check for admin sidebar request context processor dependency.

Co-authored-by: Carlton Gibson <carlton.gibson@noumenal.es>

Backport of d522b51c40 from master

tests/admin_scripts/tests.py

@@ -1124,6 +1124,7 @@ class ManageCheck(AdminScriptTestCase):
                         'APP_DIRS': True,
                         'OPTIONS': {
                             'context_processors': [
+                                'django.template.context_processors.request',
                                 'django.contrib.auth.context_processors.auth',
                                 'django.contrib.messages.context_processors.messages',
                             ],