docs: update menu demo

Author: tangjinzhou

components/menu/__tests__/__snapshots__/demo.test.js.snap

@@ -130,9 +130,14 @@ exports[`renders ./components/menu/demo/template.md correctly 1`] = `
 <div style="width: 256px;"><button type="button" class="ant-btn ant-btn-primary" style="margin-bottom: 16px;"><i class="anticon anticon-menu-fold"></i></button>
   <ul class="ant-menu ant-menu-inline ant-menu-root ant-menu-dark" role="menu">
     <li role="menuitem" class="ant-menu-item ant-menu-item-selected" style="padding-left: 24px;"><i class="anticon anticon-pie-chart"></i> <span>Option 1</span></li>
-    <li role="menuitem" class="ant-menu-submenu ant-menu-submenu-inline" menuinfo="[object Object]">
-      <div aria-haspopup="true" class="ant-menu-submenu-title" style="padding-left: 24px;"><span><i class="anticon anticon-mail"></i><span>Navigation 2</span></span><i class="ant-menu-submenu-arrow"></i></div>
-      <div></div>
+    <li role="menuitem" class="ant-menu-submenu ant-menu-submenu-inline ant-menu-submenu-open">
+      <div aria-expanded="true" aria-owns="2$Menu" aria-haspopup="true" class="ant-menu-submenu-title" style="padding-left: 24px;"><span><i class="anticon anticon-mail"></i><span>Navigation 2</span></span><i class="ant-menu-submenu-arrow"></i></div>
+      <ul class="ant-menu ant-menu-inline  ant-menu-sub" role="menu">
+        <li role="menuitem" class="ant-menu-submenu ant-menu-submenu-inline">
+          <div aria-haspopup="true" class="ant-menu-submenu-title" style="padding-left: 48px;"><span><i class="anticon anticon-mail"></i><span>Navigation 3</span></span><i class="ant-menu-submenu-arrow"></i></div>
+          <div></div>
+        </li>
+      </ul>
     </li>
   </ul>
 </div>

components/menu/demo/SubMenu.vue

@@ -1,5 +1,5 @@
 <template functional>
-  <a-sub-menu v-on="listeners" v-bind="data.attrs" :key="data.key">
+  <a-sub-menu v-on="listeners" :key="data.key">
     <span slot="title"><a-icon type="mail" /><span>{{data.attrs.menuInfo.title}}</span></span>
     <template v-for="item in data.attrs.menuInfo.children">
       <a-menu-item v-if="!item.children" :key="item.key">

components/menu/demo/template.md

@@ -18,7 +18,7 @@ The properties of `a-sub-menu` are dynamically changed inside the component. If
     </a-button>
     <a-menu
       :defaultSelectedKeys="['1']"
-      :defaultOpenKeys="['sub1']"
+      :defaultOpenKeys="['2']"
       mode="inline"
       theme="dark"
       :inlineCollapsed="collapsed"