Modernize legacy Python 2 syntax with pyupgrade.

Generated by `pyupgrade --py3-plus --keep-percent-format` followed by
manual indentation fixes.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

zulip/integrations/openshift/post_deploy

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
 #
 # Zulip notification post-receive hook.
 

zulip/integrations/openshift/zulip_openshift_config.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 # https://github.com/python/mypy/issues/1141
 from typing import Dict, Text, Optional
 
@@ -25,7 +23,7 @@ def deployment_notice_destination(branch):
     # type: (str) -> Optional[Dict[str, Text]]
     if branch in ['master', 'test-post-receive']:
         return dict(stream  = 'deployments',
-                    subject = u'%s' % (branch,))
+                    subject = '%s' % (branch,))
 
     # Return None for cases where you don't want a notice sent
     return None