chore: use reactive components count in benchmark (vuejs#7996)

Author: jonkofee

benchmarks/reorder-list/index.html

@@ -15,7 +15,7 @@
 
     <script type="text/x-template" id="t">
       <div>
-        <h1>{{ total }} Components</h1>
+        <h1>{{ items.length }} Components</h1>
         <p>{{ action }} took {{time}}ms.</p>
         <button @click="shuffle">shuffle</button>
         <button @click="add">add</button>