misc: update settings to use MIDDLEWARE (#38162)

tests/conftest.py

@@ -23,8 +23,6 @@ def app(request):
     import django
 
     wtm = django_webtest.WebTestMixin()
-    if django.VERSION >= (1, 11):
-        wtm._middleware_setting_name = 'MIDDLEWARE_CLASSES'
     wtm._patch_settings()
     request.addfinalizer(wtm._unpatch_settings)
     return django_webtest.DjangoTestApp()

welco/settings.py

@@ -54,7 +54,7 @@ INSTALLED_APPS = (
     'rest_framework',
 )
 
-MIDDLEWARE_CLASSES = (
+MIDDLEWARE = (
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',