Fix email authentication documentation

With version 4.x, the required bundle for email authentication is `symfony/swiftmailer-bundle` instead of `mailer`

Author: tobalsan

Resources/doc/providers/email.md

@@ -6,7 +6,7 @@ Email Authentication
 Install the mailer component:
 
 ```bash
-composer require mailer
+composer require symfony/swiftmailer-bundle
 ```
 
 ## How it works