httpconnection: don't use dict()

httpconnection: don't use dict()

Not sure the history here. But we don't do this elsewhere.

--- a/mercurial/httpconnection.py	Thu Mar 09 15:38:00 2017 -0800
+++ b/mercurial/httpconnection.py	Thu Mar 09 20:51:57 2017 -0800
@@ -67,13 +67,13 @@
 # moved here from url.py to avoid a cycle
 def readauthforuri(ui, uri, user):
     # Read configuration
-    config = dict()
+    config = {}
     for key, val in ui.configitems('auth'):
         if '.' not in key:
             ui.warn(_("ignoring invalid [auth] key '%s'\n") % key)
             continue
         group, setting = key.rsplit('.', 1)
-        gdict = config.setdefault(group, dict())
+        gdict = config.setdefault(group, {})
         if setting in ('username', 'cert', 'key'):
             val = util.expandpath(val)
         gdict[setting] = val