Backport #23558
There are still many dropdowns using fomantic icon. For example: new
issue with issue template.
Avoid polluting the fomantic styles.
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Backport #23560 by @wxiaoguang
1. The "close" inside "modal" are likely broken for long time
* There is no var called `--body-color`
* There is no `fullscreen modal`
* The `.ui.modal > .close.inside` doesn't seem to match most icons. It
only matches a few like "fork-repo-modal" or "adopt repo". Other places
are just buggy code copied again and again.
2. Convert the legacy `&:hover` LESS syntax to CSS syntax
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: delvh <leon@kske.dev>
