[web] everything old is new again
Kill the "new" cubicweb.css, and move cubicweb.old.css back in its
place. Closes #4763360.
<div id="ajaxroot">
<div class="ajaxHtmlHead">
<script src="http://foo.js" type="text/javascript"> </script>
<link rel="stylesheet" type="text/css" media="all" href="qunit.css" />
</div>
<h1>Hello</h1>
</div>