fix pep 0234 link in performance/iteritems page

Author: drgarcia1986

docs/performance/not_using_iteritems_to_iterate_large_dict.rst

@@ -34,4 +34,4 @@ The updated code below uses ``iteritems()`` instead of ``items()`` method. Note
 
 References
 ----------
-- `PEP 234 Iterators <https://www.python.org/dev/peps/pep-0234://www.python.org/dev/peps/pep-0234/>`_
+- `PEP 234 Iterators <https://www.python.org/dev/peps/pep-0234/>`_