Remove urls.py from startapp blog file listing. Fix DjangoGirls#1535

Fixes DjangoGirls#1535. `python manage.py startapp blog` doesn’t create this file: https://stackoverflow.com/questions/45002225/why-isnt-urls-py-generated-with-django-admin-startapp-mysite

Author: thibaudcolas

en/django_models/README.md

@@ -88,7 +88,6 @@ djangogirls
 │   │   └── __init__.py
 │   ├── models.py
 │   ├── tests.py
-|   ├── urls.py
 │   └── views.py
 ├── db.sqlite3
 ├── manage.py