Fixed the path to the admin's compress.py script in the doc.

To simplify the process of providing optimized javascript code, Django

includes a handy script which should be used to create a "minified" version.

This script is located at ``django/contrib/admin/static/js/compress.py``.

This script is located at ``django/contrib/admin/static/admin/js/compress.py``.

Behind the scenes, ``compress.py`` is a front-end for Google's

`Closure Compiler`_ which is written in Java. However, the Closure Compiler