Review the 'xubuntu' manual testing story

[Hyask]

Context

This repo is based on a dump of the content of https://iso.qa.ubuntu.com/.

That content is quite old and hasn't been refreshed in a while, so let's take
the occasion to review the manual testing story of every product, both Canonical
and community Flavors.

Acceptance criteria

• The content of noble/xubuntu has been verified and is up to date.
• The content of resolute/xubuntu has been verified and is up to date.
• All the test cases involved in xubuntu have been verified to display correctly when previewed (no more broken HTML).