minor #11739 Uncomment code and add info (OskarStark)

This PR was merged into the 3.4 branch.

Discussion
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Uncomment code and add info

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Commits
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d78f17d Uncomment code and add info

Author: javiereguiluz

email.rst

@@ -114,16 +114,15 @@ an email is pretty straightforward::
                 ),
                 'text/html'
             )
-            /*
-             * If you also want to include a plaintext version of the message
+
+            // you can remove the following code if you don't define a text version for your emails
             ->addPart(
                 $this->renderView(
                     'Emails/registration.txt.twig',
                     ['name' => $name]
                 ),
                 'text/plain'
             )
-            */
         ;
 
         $mailer->send($message);