finished quick start about database [skip ci]

config/web.php

@@ -1,7 +1,6 @@
 <?php
 
 $params = require(__DIR__ . '/params.php');
-$db = require(__DIR__ . '/db.php');
 
 $config = [
     'id' => 'basic',
@@ -32,7 +31,7 @@ $config = [
                 ],
             ],
         ],
-        'db' => $db,
+        'db' => require(__DIR__ . '/db.php'),
     ],
     'params' => $params,
 ];