fix(product-gift): 修复 toggleGift 后多余逗号语法错误

cfc-frontend/pages/discover-detail/product-detail/product-detail.vue

@@ -585,7 +585,7 @@ export default {
     },
     toggleGift: function(item) {
       this.$set(item, '_selected', !item._selected)
-    },,
+    },
 
     onBuy: function() {
       var userId = uni.getStorageSync('userId')