Add transparent background to remove button in tree item list

app/assets/stylesheets/components/related_items_list.scss

@@ -213,6 +213,7 @@ $item-remove-button-space: 42px;
   margin-right: $gl-padding-4 / 2;
   line-height: 0;
   border-color: transparent;
+  background-color: transparent;
   color: $gl-text-color-secondary;
 
   .related-items-tree & {

changelogs/unreleased/remove-tree-item-btn-background.yml

+---
+title: Add transparent background to remove button in tree item list
+merge_request: 38597
+author:
+type: fixed