Remove fomantic list module (#30281)

Likely still some unnecessary CSS but any combinations with the `ui
list` classes are covered. There was only on instance of `horizontal
list` which I removed. It was this part of the commit page:

<img width="396" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/c49ec4f5-93c3-41d6-a907-cdbedf8abc44">

web_src/css/index.css

@@ -8,6 +8,7 @@
 @import "./modules/header.css";
 @import "./modules/input.css";
 @import "./modules/label.css";
+@import "./modules/list.css";
 @import "./modules/segment.css";
 @import "./modules/grid.css";
 @import "./modules/message.css";