Remove fomantic accordion module (#15951)

Replace it with native <detail> element. Did some slight restyling on
the release downloads, new behaviour should be exactly the same
otherwise.

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/js/index.js

@@ -2563,7 +2563,6 @@ $(document).ready(async () => {
     direction: 'upward',
     fullTextSearch: 'exact'
   });
-  $('.ui.accordion').accordion();
   $('.ui.checkbox').checkbox();
   $('.ui.progress').progress({
     showActivity: false