Removed cases of six.iter* wrapped in a list()

There's absolutely no advantage [and a mild performance hit] to using six.iter*
in these cases.

django/template/base.py

@@ -1097,7 +1097,7 @@ def parse_bits(parser, bits, params, varargs, varkw, defaults,
         kwarg = token_kwargs([bit], parser)
         if kwarg:
             # The kwarg was successfully extracted
-            param, value = list(six.iteritems(kwarg))[0]
+            param, value = kwarg.popitem()
             if param not in params and varkw is None:
                 # An unexpected keyword argument was supplied
                 raise TemplateSyntaxError(