Fix typo in documentation (#136)

docs/content/en/usage.md

@@ -58,6 +58,7 @@ async asyncData({ $http }) {
 async asyncData({ $http }) {
   const users = await $http.$get('https://reqres.in/api/users')
   return { users }
+}
 ```
 
 
@@ -96,4 +97,4 @@ For store actions you can also use `this.$http`:
     }
   }
 }
-```
+```