[Glitch] Fix low-contrast hover colour of alert actions (light theme only)

Port 28a42bb62c to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/styles/components.scss

@@ -10748,7 +10748,7 @@ noscript {
   &:hover,
   &:focus,
   &:active {
-    background: color.change($ui-base-color, $alpha: 0.85);
+    background: color.change($white, $alpha: 0.15);
   }
 }