remove remaining Icon class

Co-authored-by: Hugo Alliaume <hugo@alliau.me>

Author: smnandre

ux.symfony.com/templates/ux_packages/swup.html.twig

@@ -52,7 +52,7 @@
 
     <div class="d-flex eyebrows pt-3 align-items-center justify-content-center flex-wrap">
         <div>Ajax-powered page navigation</div>
-        <twig:ux:icon name="circle-fill" class="Icon" />
+        <twig:ux:icon name="circle-fill" />
         <div>URL in address bar changes</div>
         <twig:ux:icon name="circle-fill" class="Icon" />
         <div>Customizable transitions</div>