fix(Sku): preview when disable (#6641)

Co-authored-by: songweite <songweite@youzan.com>

src/sku/index.less

@@ -194,6 +194,7 @@
             position: absolute;
             top: 0;
             right: 0;
+            z-index: 3;
             width: 18px;
             height: 18px;
           }