Remove unused import

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/migrations/0040_auto_20150818_1643.py

 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from django.db import models, migrations
+from django.db import migrations
 import weblate.trans.fields