Remove fomantic checkbox module (#30162)

CSS is pretty slim already and the `.ui.toggle.checkbox` sliders on
admin page also still work. The only necessary JS is the one that links
`input` and `label` so that it can be toggled via label. All checkboxes
except the markdown ones render at `--checkbox-size: 16px` now.

<img width="174" alt="Screenshot 2024-03-28 at 22 15 10"
src="https://github.com/go-gitea/gitea/assets/115237/3455c1bb-166b-47e4-9847-2d20dd1f04db">

<img width="499" alt="Screenshot 2024-03-28 at 21 00 07"
src="https://github.com/go-gitea/gitea/assets/115237/412be2b3-d5a0-478a-b17b-43e6bc12e8ce">

<img width="83" alt="Screenshot 2024-03-28 at 22 14 34"
src="https://github.com/go-gitea/gitea/assets/115237/d8c89838-a420-4723-8c49-89405bb39474">

---------

Co-authored-by: delvh <dev.lh@web.de>

web_src/css/modules/animations.css

@@ -6,7 +6,6 @@
 .is-loading {
   pointer-events: none !important;
   position: relative !important;
-  overflow: hidden !important;
 }
 
 .is-loading > * {