Fix JavaScript error on pages with a TOC

When loading a documentation page with a table of contents (e.g.
https://www.raspberrypi.com/documentation/computers/getting-started.html),
the following JavaScript error is thrown in the console:

    TypeError: e.indexOf is not a function. (In 'e.indexOf(" ")',
    'e.indexOf' is undefined)

This is caused by a unsupported mix of dependencies for Tocify:
specifically, we're attempting to load jQuery 3.6.0 which removed an API
used by Tocify (see
gfranko/jquery.tocify.js#103).

Fix this by loading versions of jQuery and jQuery UI that are supported
by Tocify.

jekyll-assets/_includes/scripts.html

@@ -2,8 +2,8 @@
 <script src="{{ site.baseurl }}/scripts/nav.js" type="text/javascript"></script>
 
 <!-- TOCify scripts -->
-<script src="{{ site.baseurl }}/scripts/jquery-3.6.0.min.js"></script>
-<script src="{{ site.baseurl }}/scripts/jquery-ui-1.9.1.custom.min.js"></script>
+<script src="{{ site.baseurl }}/scripts/jquery-1.12.4.min.js"></script>
+<script src="{{ site.baseurl }}/scripts/jquery-ui-1.13.0.custom.min.js"></script>
 <script src="{{ site.baseurl }}/scripts/jquery.tocify.min.js"></script>
 
 <!-- Copy To Clipboard scripts -->