docs(menu): update example to new activator syntax

Author: johnleider

packages/docs/src/examples/accessibility/menu.vue

@@ -1,26 +1,21 @@
 <template>
   <div class="text-center">
     <v-menu>
-      <template v-slot:activator="{ on, attrs }">
-        <v-btn
-          v-bind="attrs"
-          v-on="on"
-        >
-          Click me
-        </v-btn>
+      <template v-slot:activator="{ props: activatorProps }">
+        <v-btn text="Click me" v-bind="activatorProps"></v-btn>
       </template>
 
       <v-list>
         <v-list-item @click="onClick">
-          <v-list-item-title>Option 1</v-list-item-title>
+          <v-list-item-title title="Option 1"></v-list-item-title>
         </v-list-item>
 
         <v-list-item disabled>
-          <v-list-item-title>Option 2</v-list-item-title>
+          <v-list-item-title title="Option 2"></v-list-item-title>
         </v-list-item>
 
         <v-list-item @click="onClick">
-          <v-list-item-title>Option 3</v-list-item-title>
+          <v-list-item-title title="Option 3"></v-list-item-title>
         </v-list-item>
       </v-list>
     </v-menu>