docs: Fix LocelProvider demo

components/locale-provider/demo/all.md

@@ -17,9 +17,9 @@ Components which need localization support are listed here, you can toggle the l
 import { LocaleProvider, Pagination, DatePicker, TimePicker, Calendar,
          Popconfirm, Table, Modal, Button, Select, Transfer, Radio } from 'antd';
 import zhCN from 'antd/lib/locale-provider/zh_CN';
+import enUS from 'antd/lib/locale-provider/en_US';
 import moment from 'moment';
 import 'moment/locale/zh-cn';
-moment.locale('en');
 
 const Option = Select.Option;
 const RangePicker = DatePicker.RangePicker;
@@ -108,25 +108,20 @@ class App extends React.Component {
   constructor() {
     super();
     this.state = {
-      locale: null,
+      locale: enUS,
     };
   }
   changeLocale = (e) => {
     const localeValue = e.target.value;
     this.setState({ locale: localeValue });
-    if (!localeValue) {
-      moment.locale('en');
-    } else {
-      moment.locale('zh-cn');
-    }
   }
   render() {
     return (
       <div>
         <div className="change-locale">
           <span style={{ marginRight: 16 }}>Change locale of components: </span>
-          <Radio.Group defaultValue={null} onChange={this.changeLocale}>
-            <Radio.Button key="en" value={null}>English</Radio.Button>
+          <Radio.Group defaultValue={enUS} onChange={this.changeLocale}>
+            <Radio.Button key="en" value={enUS}>English</Radio.Button>
             <Radio.Button key="cn" value={zhCN}>中文</Radio.Button>
           </Radio.Group>
         </div>