hide release candidate call to action

Keeping it commented so we can reuse it on future releases

Author: dlech

downloads.md

@@ -20,19 +20,18 @@ redirect_from: /download/
         </p>
     </div>
 </div>
-<div class="row margin-bottom-xl">
+<!-- <div class="row margin-bottom-xl">
     <div class="col-sm-12">
         <div class="alert alert-info">
             <div class="lead">
                 {% include /style/icon.html type="info" %}
                 ev3dev-stretch R3 is almost ready!
             </div>
-            
             Please help test the next release of ev3dev.
             <a class="alert-link" href="/news/2020/03/11/ev3dev-stretch-r3-release-candidate">Follow this link for more information.</a>.
         </div>
     </div>
-</div>
+</div> -->
 <div class="row margin-bottom-xl">
     <div class="col-sm-8">
         <div class="margin-bottom-md">