[1.7.x] Removed unnecessary absolute_imports.

Backport of e0cf030194 from master

tests/apps/tests.py

@@ -1,4 +1,4 @@
-from __future__ import absolute_import, unicode_literals
+from __future__ import unicode_literals
 
 import os
 import sys

tests/contenttypes_tests/tests.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-from __future__ import absolute_import, unicode_literals
+from __future__ import unicode_literals
 
 import sys
 

tests/schema/tests.py

@@ -1,4 +1,3 @@
-from __future__ import absolute_import
 import datetime
 import unittest