Modify the use case of the afterRemoval interface in the util module in the...

Modify the use case of the afterRemoval interface in the util module in the docs document to become popular
Signed-off-by: Nbi-hu <bihu@huawei.com>
https://gitee.com/openharmony/docs/issues/I5RWJK

zh-cn/application-dev/reference/apis/js-apis-util.md

@@ -1145,7 +1145,7 @@ afterRemoval(isEvict: boolean,key: K,value: V,newValue: V): void
 **示例：**
   ```js
   let arr = [];
-  class ChildLruBuffer extends util.LruBuffer
+  class ChildLruBuffer<K, V> extends util.LruBuffer<K, V>
   {
   	constructor()
   	{