add noscript notice to the releases page

static/releases.html

@@ -47,6 +47,8 @@
             it's not possible to downgrade unless a downgrade update package is generated, so use
             the Stable channel if you cannot tolerate dealing with temporary issues while a new
             release for the Beta channel is being created.</p>
+            <noscript><strong>JavaScript is required to fetch the current list of releases from
+            the update server.</strong></noscript>
             <h2>Stable channel</h2>
             <div id="stable"></div>
             <h2>Beta channel</h2>