Issue 6769 - Avoid hardcoding the URL

pages/filters/popup.tmpl

 title = $popup
 template = testcase
 
 {% set testcase_moreinfo = [
   ("Filter Options", "https://adblockplus.org/filters#options"),
 ] %}
 
 
 <script>
 function do_popup()
 {
    window.open("/en/popuptarget")
 }
 </script>
 
 <section class="site-panel">
   <h2>$popup</h2>
   <p>Check that usage of the $popup filter option is working as expected.</p>
   <p>With the filter displayed below each test case added to ABP (or with the testcase subscription installed and active), the popups triggered by the link/buttons below should be blocked/closed.</p>
 </section>
 
 <section class="site-panel">
   <h2>Link-based popup</h2>
   <div class="testcase-container">
     <a href="/en/popuptarget" target="_blank">Link popup</a><br><br>
   </div>
   <h3>Filters</h3>
-  <pre>||testpages.adblockplus.org/en/popuptarget^$popup</pre>
+  <pre>||{{ site_url|strip_proto }}/en/popuptarget^$popup</pre>
 </section>
 
 <section class="site-panel">
   <h2>Script-based popup</h2>
   <div class="testcase-container">
     <button onclick="do_popup();">window.open() popup</button>
   </div>
   <h3>Filters</h3>
-  <pre>||testpages.adblockplus.org/en/popuptarget^$popup</pre>
-</section>
+  <pre>||{{ site_url|strip_proto }}/en/popuptarget^$popup</pre>
+</section>