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/git/post-receive

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

zulip/integrations/git/zulip_git_config.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 #
 from typing import Dict, Text, Optional
 
@@ -28,7 +27,7 @@ def commit_notice_destination(repo, branch, commit):
     # type: (Text, Text, Text) -> Optional[Dict[Text, Text]]
     if branch in ["master", "test-post-receive"]:
         return dict(stream  = STREAM_NAME,
-                    subject = u"%s" % (branch,))
+                    subject = "%s" % (branch,))
 
     # Return None for cases where you don't want a notice sent
     return None