Fix rubric directive typo in modules/zend.filter.uri-normalize.rst

This fixes a ```reST``` ```rubric``` directive typo in ```modules/zend.filter.uri-normalize.rst```. The following error can be seen in previous build outputs:

>modules/zend.filter.uri-normalize.rst:11: ERROR: Unknown directive type "rubrice".

You may confirm that the above errors no longer exist from the Travis-ci build details link below and the [build log](https://s3.amazonaws.com/archive.travis-ci.org/jobs/12473243/log.txt "Build Log") and that the documentation still renders as expected: http://webdevelzf2-documentation.readthedocs.org/en/latest/.