minor #5240 [Cookbook][Email] revert #4808 (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Cookbook][Email] revert #4808

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4884

Commits
-------

b1e8d54 revert #4808

cookbook/email/email.rst

@@ -93,9 +93,8 @@ an email is pretty straightforward::
 
     public function indexAction($name)
     {
-        $mailer = $this->get('mailer');
-        $message = $mailer->createMessage()
-            ->setSubject('You have Completed Registration!')
+        $message = \Swift_Message::newInstance()
+            ->setSubject('Hello Email')
             ->setFrom('[email protected]')
             ->setTo('[email protected]')
             ->setBody(
@@ -117,7 +116,7 @@ an email is pretty straightforward::
             )
             */
         ;
-        $mailer->send($message);
+        $this->get('mailer')->send($message);
 
         return $this->render(...);
     }