docs: update tabs & menu demo

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

@@ -170,9 +170,6 @@ exports[`renders ./components/menu/demo/switch-mode.md correctly 1`] = `
 
 exports[`renders ./components/menu/demo/theme.md correctly 1`] = `
 <div>
-  <md>
-    ## 主题 内建了两套主题 \`light|dark\`，默认 \`light\`。
-  </md>
   <label class="ant-checkbox-wrapper"><span class="ant-checkbox"><input type="checkbox" class="ant-checkbox-input"><span class="ant-checkbox-inner"></span></span>
   </label> Change Theme
   <br>

components/menu/demo/theme.md

@@ -11,10 +11,6 @@ There are two built-in themes: 'light' and 'dark'. The default value is 'light'.
 ```html
 <template>
 <div>
-  <md>
-  ## 主题
-  内建了两套主题 `light|dark`，默认 `light`。
-  </md>
   <a-checkbox @change="changeTheme" /> Change Theme
   <br />
   <br />

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

@@ -2,9 +2,6 @@
 
 exports[`renders ./components/tabs/demo/basic.md correctly 1`] = `
 <div>
-  <md>
-    ## 基本 默认选中第一项。
-  </md>
   <div class="ant-tabs ant-tabs-top ant-tabs-line">
     <div role="tablist" tabIndex="0" class="ant-tabs-bar">
       <div class="ant-tabs-extra-content" style="float:right;"></div>

components/tabs/demo/basic.md

@@ -12,10 +12,6 @@ Default activate first tab.
 
 <template>
 <div>
-  <md>
-    ## 基本
-    默认选中第一项。
-  </md>
   <a-tabs defaultActiveKey="1" @change="callback">
     <a-tab-pane tab="Tab 1" key="1">Content of Tab Pane 1</a-tab-pane>
     <a-tab-pane tab="Tab 2" key="2" forceRender>Content of Tab Pane 2</a-tab-pane>