docs: Update responsive.md (#27604)

Add missing dimension `xxl` to en-US.

components/grid/demo/responsive.md

@@ -7,11 +7,11 @@ title:
 
 ## zh-CN
 
-参照 Bootstrap 的 [响应式设计](http://getbootstrap.com/css/#grid-media-queries)，预设六个响应尺寸：`xs` `sm` `md` `lg` `xl`  `xxl`。
+参照 Bootstrap 的 [响应式设计](http://getbootstrap.com/css/#grid-media-queries)，预设六个响应尺寸：`xs` `sm` `md` `lg` `xl` `xxl`。
 
 ## en-US
 
-Referring to the Bootstrap [responsive design](http://getbootstrap.com/css/#grid-media-queries), here preset six dimensions: `xs` `sm` `md` `lg` `xl`.
+Referring to the Bootstrap [responsive design](http://getbootstrap.com/css/#grid-media-queries), here preset six dimensions: `xs` `sm` `md` `lg` `xl` `xxl`.
 
 ```jsx
 import { Row, Col } from 'antd';