Remove urlpatterns from url file

urlpatterns has been deprecated since Django 1.8 and has been
removed in 1.10 (the current version horizon master is on).
Source: https://docs.djangoproject.com/en/1.10/releases/1.8/#django-conf-urls-patterns

Change-Id: Iaf14e7401908f30093ffc6014f5efe46e525c57f

distil_ui/content/billing/urls.py

@@ -12,12 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from django.conf.urls import patterns  # noqa
 from django.conf.urls import url  # noqa
 
 from distil_ui.content.billing import views
 
-urlpatterns = patterns(
-    '',
+urlpatterns = [
     url(r'^$', views.IndexView.as_view(), name='index'),
-)
+]