Fix syntax highlighting

lstrojny · lstrojny · commit 1a0485a1367a · 2016-04-27T21:25:58.000+02:00
diff --git a/doc/stubbing.md b/doc/stubbing.md
@@ -83,7 +83,7 @@ $this->http->mock
     ->then()
         ->body('response')
     ->end();`
-``
+```
 
 ## Limiting
 
