change close button style

assets/css/style.scss

@@ -31,6 +31,10 @@ $list-group-action-color: var(--text-primary-color);
 // Cards
 $card-bg: var(--background-color-secondary);
 
+// Close button
+$close-color: var(--text-primary-color);
+$close-font-weight: 500;
+
 @import 'font';
 @import 'bootstrap';