Don’t show cancelled jobs anywhere

The information about a job doesn’t make sense if a job is cancelled.

We could change the information to reflect that the job won’t be sent/
wasn’t sent/was cancelled, but there’s nothing you can really do with
this info.

So instead let’s:
- hide cancelled jobs from the dashboard
- hide cancelled jobs from the jobs page
- 404 the page if the user tries to click back enough times to hit the
  job page

tests/app/main/views/test_jobs.py

@@ -149,6 +149,25 @@ def test_should_show_scheduled_job(
         assert page.find('main').find_all('p')[2].text.strip() == 'Sending will start at midnight'
 
 
+def test_should_not_show_cancelled_job(
+    app_,
+    service_one,
+    active_user_with_permissions,
+    mock_get_cancelled_job,
+    mocker,
+    fake_uuid
+):
+    with app_.test_request_context(), app_.test_client() as client:
+        client.login(active_user_with_permissions, mocker, service_one)
+        response = client.get(url_for(
+            'main.view_job',
+            service_id=service_one['id'],
+            job_id=fake_uuid
+        ))
+
+        assert response.status_code == 404
+
+
 def test_should_show_not_show_csv_download_in_tour(
     app_,
     service_one,