doc: update grid demo

Author: tangjinzhou

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

@@ -238,14 +238,12 @@ exports[`renders ./components/grid/demo/playfround.vue correctly 1`] = `
   <a-col :span="6"/>
   <a-col :span="6"/>
   <a-col :span="6"/>
-</a-row>
-    </pre><pre>&lt;a-row :gutter="[16,16]"&gt;
+&lt;/a-row&gt;</pre><br><pre>&lt;a-row :gutter="[16,16]"&gt;
   &lt;a-col :span="6"/&gt;
   &lt;a-col :span="6"/&gt;
   &lt;a-col :span="6"/&gt;
   &lt;a-col :span="6"/&gt;
-&lt;/a-row&gt;
-    </pre>
+&lt;/a-row&gt;</pre>
 </div>
 `;
 

components/grid/demo/playfround.vue

@@ -67,13 +67,9 @@ A simple playground for column count and gutter.
         <div>Column</div>
       </a-col>
     </a-row>
-    <pre
-      >{{ rowColHtml }}
-    </pre>
+    <pre>{{ rowColHtml }}</pre>
     <br />
-    <pre
-      >{{ rowColHtml }}
-    </pre>
+    <pre>{{ rowColHtml }}</pre>
   </div>
 </template>
 <script lang="ts">