add django.contrib.contenttypes to all tests by default

test-data/typecheck/fields/test_generic_foreign_key.yml

@@ -8,7 +8,6 @@
         Tag.objects.create(content_object=myuser)
         reveal_type(Tag().content_object)  # N: Revealed type is 'Union[Any, None]'
     installed_apps:
-        - django.contrib.contenttypes
         - myapp
     files:
         -   path: myapp/__init__.py

test-data/typecheck/fields/test_related.yml

@@ -25,7 +25,6 @@
         reveal_type(book.publisher_id)  # N: Revealed type is 'builtins.int*'
         reveal_type(book.owner_id)  # N: Revealed type is 'builtins.int*'
     installed_apps:
-        - django.contrib.contenttypes
         - django.contrib.auth
         - myapp
     files:

test-data/typecheck/test_config.yml

@@ -30,7 +30,6 @@
         mymodel = MyModel(user_id=1)
         reveal_type(mymodel.id)  # N: Revealed type is 'builtins.int*'
     installed_apps:
-        - django.contrib.contenttypes
         - django.contrib.auth
         - myapp
     files: