Move `z-index` to .list-group-item-action and remove redundant `text-decoration: none` (#27996)

scss/_list-group.scss

@@ -24,6 +24,7 @@
 
   // Hover state
   @include hover-focus {
+    z-index: 1; // Place hover/focus items above their siblings for proper border styling
     color: $list-group-action-hover-color;
     text-decoration: none;
     background-color: $list-group-hover-bg;
@@ -58,11 +59,6 @@
     @include border-bottom-radius($list-group-border-radius);
   }
 
-  @include hover-focus {
-    z-index: 1; // Place hover/active items above their siblings for proper border styling
-    text-decoration: none;
-  }
-
   &.disabled,
   &:disabled {
     color: $list-group-disabled-color;