wsgicgi: switch the default PATH_INFO back to str

It looks like everything here is meant to be str, and regressed in 687b865b95ad.
Pytype didn't flag this, but is really confused about the range of possible
types for the dictionary values, and flagged missing `lower()` on various types
in this area.

Differential Revision: https://phab.mercurial-scm.org/D10204

mercurial/hgweb/wsgicgi.py

@@ -25,7 +25,7 b' def launch(application):'
     procutil.setbinary(procutil.stdout)
 
     environ = dict(pycompat.iteritems(os.environ))  # re-exports
-    environ.setdefault('PATH_INFO', b'')
+    environ.setdefault('PATH_INFO', '')
     if environ.get('SERVER_SOFTWARE', '').startswith('Microsoft-IIS'):
         # IIS includes script_name in PATH_INFO
         scriptname = environ['SCRIPT_NAME']