docs: prevent UNotifications slot #description override

Otherwise it alters the display of the Notification examples where actions moves under the title.

docs/app.vue

@@ -17,10 +17,6 @@
       <template #title="{ title }">
         <span v-html="title" />
       </template>
-
-      <template #description="{ description }">
-        <span v-html="description" />
-      </template>
     </UNotifications>
   </div>
 </template>