app_notes: fix link to packaging guide (AppImage#3197)

Author: Igor-Misic

_includes/app_notes.html

@@ -44,7 +44,7 @@ <h3>Pro Tips for further enhancing the {{ page.name | remove: ".md" }} AppImage<
     <p>Thanks for shipping AppStream metainfo inside your AppImage. Please open a pull request on <a href="https://github.com/AppImage/appimage.github.io/blob/master/data/{{ page.name | remove: ".md" }}">https://github.com/AppImage/appimage.github.io/blob/master/data/{{ page.name | remove: ".md" }}</a> if you have changed it and would like to see this page updated accordingly.</p>
 {% else %}
     <p>Improve this entry by shipping an <a href="https://docs.appimage.org/packaging-guide/optional/appstream.html">AppStream metainfo file</a> inside the AppImage in the <code>usr/share/metainfo</code> directory. There is an <a href="https://appimage.github.io/simple-appstream-generator/">online tool</a> that makes it easy to make one.</p>
-    <p>The screenshot for {{ page.name | remove: ".md" }} has been automatically taken during a fully automated test. You can specify the URL to a nicer one by shipping an <a href="https://docs.appimage.org/packaging-guide/appstream.html">AppStream metainfo file</a>.</p>
+    <p>The screenshot for {{ page.name | remove: ".md" }} has been automatically taken during a fully automated test. You can specify the URL to a nicer one by shipping an <a href="https://docs.appimage.org/packaging-guide/index.html">AppStream metainfo file</a>.</p>
 {% endif %}
 
 {% if post.appdata.Url.donation %}