Add type hint for UserFactory (#5312)

Since factory-boy 3.3.1, we can type annotate factories:

https://github.com/FactoryBoy/factory_boy/pull/1059

Setting that up for the only factory of the project

{{cookiecutter.project_slug}}/{{cookiecutter.project_slug}}/users/tests/factories.py

@@ -8,7 +8,7 @@ from factory.django import DjangoModelFactory
 from {{ cookiecutter.project_slug }}.users.models import User
 
 
-class UserFactory(DjangoModelFactory):
+class UserFactory(DjangoModelFactory[User]):
     {%- if cookiecutter.username_type == "username" %}
     username = Faker("user_name")
     {%- endif %}