Update selenium link in context.xml

A project created using the archetype contains a link in conf/context.xml to a documentation page about creating a Selenium test case. The link points to the 7.8-version of the page which is no longer publicly available. It should point to the latest version: https://www.onehippo.org/library/development/create-a-selenium-test-case.html

The file in git:

https://code.onehippo.org/cms-community/hippo-project-archetype/blob/hippo-project-archetype-4.1.0/src/main/resources/archetype-resources/conf/context.xml

The relevant snippet:

    <!-- Enable this to let wicket output a wicketpath attribute for elements,
         see: http://www.onehippo.org/7_8/library/development/create-a-selenium-test-case.html -->
    <!--
    <Parameter name="output-wicketpaths" value="true"/>
    -->