Show rejected broadcasts on ‘Previous alerts’ page

Two reasons to not hide rejected broadcasts:
- if a broadcast was rejected by mistake then it’s useful to have an
  audit of who did that
- it means you can still see old broadcasts without having to leave
  in pending-approval, which is dangerous because they might
  accidentally be approved

tests/conftest.py

@@ -4420,6 +4420,13 @@ def mock_get_broadcast_messages(
                     datetime.utcnow() - timedelta(days=10)
                 ).isoformat(),
             ),
+            partial_json(
+                id_=uuid4(),
+                status='rejected',
+                updated_at=(
+                    datetime.utcnow() - timedelta(hours=1)
+                ).isoformat(),
+            ),
         ]
 
     return mocker.patch(