docs: fix factory classname

Author: kenjis

user_guide_src/source/database/utilities/001.php

@@ -1,7 +1,7 @@
 <?php
 
 $db     = db_connect();
-$dbutil = \CodeIgniter\Database\Config::utils();
+$dbutil = \Config\Database::utils();
 
 $query = $db->query('SELECT * FROM mytable');
 

user_guide_src/source/database/utilities/002.php

@@ -1,3 +1,3 @@
 <?php
 
-$dbutil = \CodeIgniter\Database\Config::utils();
+$dbutil = \Config\Database::utils();

user_guide_src/source/database/utilities/003.php

@@ -1,3 +1,3 @@
 <?php
 
-$dbutil = \CodeIgniter\Database\Config::utils('group_name');
+$dbutil = \Config\Database::utils('group_name');