[web/test] Update mock ajax reply from "render" ajaxfunc CubicWeb transforms add_js() calls in AJAX context to <cubicweb:script> tags since ede740bd7077 and cd5738fc440f. Related to #5533303.

<div id="ajaxroot">
  <div class="ajaxHtmlHead">
    <cubicweb:script src="http://foo.js" type="text/javascript"> </cubicweb:script>
  </div>
  <h1>Hello</h1>
</div>