docs: imporve sample code

Author: kenjis

user_guide_src/source/concepts/factories.rst

@@ -59,6 +59,7 @@ In the following code, if you have ``App\Models\UserModel``, the instance will b
 Or you could also request a specific class:
 
 .. literalinclude:: factories/002.php
+   :lines: 2-
 
 If you have only ``Blog\Models\UserModel``, the instance will be returned.
 But if you have both ``App\Models\UserModel`` and ``Blog\Models\UserModel``,
@@ -67,6 +68,7 @@ the instance of ``App\Models\UserModel`` will be returned.
 If you want to get ``Blog\Models\UserModel``, you need to disable the option ``preferApp``:
 
 .. literalinclude:: factories/010.php
+   :lines: 2-
 
 See :ref:`factories-options` for the details.
 

user_guide_src/source/concepts/factories/003.php

@@ -1,5 +1,7 @@
 <?php
 
+use CodeIgniter\Config\Factories;
+
 class SomeOtherClass
 {
     public function someFunction()