Fixed a use of old url template tag in an admin template.

This was missed from r14643. I grepped for other instances and this was the
only one missing that I could find.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14777 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/admin/templates/admin/change_form.html

 {% extends "admin/base_site.html" %}
 {% load i18n admin_modify adminmedia %}
+{% load url from future %}
 
 {% block extrahead %}{{ block.super }}
-{% url admin:jsi18n as jsi18nurl %}
+{% url 'admin:jsi18n' as jsi18nurl %}
 <script type="text/javascript" src="{{ jsi18nurl|default:"../../../jsi18n/" }}"></script>
 {{ media }}
 {% endblock %}