Use English in example of global-computed.md (#1621)

packages/docs/docs/guide/global-computed.md

@@ -9,7 +9,7 @@ This is the `$site` value of the website you see now:
 ``` json
 {
   "title": "VuePress",
-  "description": "Vue 驱动的静态网站生成器",
+  "description": "Vue-powered static site generator",
   "base": "/",
   "pages": [
     {