feat: 更新 textarea 组件

pages/component/textarea/textarea.wxml

@@ -5,12 +5,12 @@
   <template is="head" data="{{title: 'textarea'}}"/>
 
   <view class="page-body">
-    <!-- <view class="page-section">
+    <view class="page-section">
       <view class="page-section-title">输入区域高度自适应，不会出现滚动条</view>
       <view class="textarea-wrp">
         <textarea bindblur="bindTextAreaBlur" auto-height />
       </view>
-    </view> -->
+    </view>
 
     <view class="page-section">
       <view class="page-section-title">这是一个可以自动聚焦的textarea</view>