portal-api-reference: Drop the script and add a line of manual redirect

Author: bbhtt

docs/portal-api-reference.rst

@@ -6,4 +6,10 @@ Portal API Reference
 .. raw:: html
 
    <meta http-equiv="refresh" content="0; url=https://flatpak.github.io/xdg-desktop-portal/docs/" />
-   <script>window.location.href = 'https://flatpak.github.io/xdg-desktop-portal/docs/'</script>
+   <noscript>
+     <p>If you are not redirected, please visit
+     <a href="https://flatpak.github.io/xdg-desktop-portal/docs/">
+       https://flatpak.github.io/xdg-desktop-portal/docs/
+     </a>.
+     </p>
+   </noscript>