Remove fomantic transition module (#26469)

Removes all dropdown and dimmer animations. Works everywhere as far as I
can tell, but need to give this thorough testing. Removes around 70kb
JS/CSS.

Note, I'm not 100% sure regarding the various callbacks, those will need
more investigation, but it appears to work nonetheless.

Fixes: https://github.com/go-gitea/gitea/issues/15709

web_src/css/modules/animations.css

@@ -105,3 +105,9 @@ code.language-math.is-loading::after {
 .pulse {
   animation: pulse 2s linear;
 }
+
+.ui.modal {
+  animation-name: fadein;
+  animation-duration: 300ms;
+  animation-timing-function: ease-in-out;
+}