docs: add // ... in sample code

To show the code is not the whole class code.

Author: kenjis

user_guide_src/source/tutorial/news_section/004.php

@@ -19,4 +19,6 @@ public function index()
             . view('news/overview')
             . view('templates/footer');
     }
+
+    // ...
 }

user_guide_src/source/tutorial/news_section/006.php

@@ -6,6 +6,8 @@
 
 class News extends BaseController
 {
+    // ...
+
     public function view($slug = null)
     {
         $model = model(NewsModel::class);