zerver/lib: Remove from __future__ import *.

zerver/lib/bugdown/testing_mocks.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-from __future__ import unicode_literals
 
 from typing import Any, Dict, Optional, Text
 import ujson

zerver/lib/statistics.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-from __future__ import division
 
 from zerver.models import UserProfile, UserActivity, UserActivityInterval, Message
 

zerver/lib/utils.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-from __future__ import division
 
 from typing import Any, Callable, List, Optional, Sequence, TypeVar, Iterable, Set, Tuple, Text
 from six import binary_type