[DependencyInjection] Fix code example

service_container.rst

@@ -407,12 +407,11 @@ example, suppose you want to make the admin email configurable:
       class SiteUpdateManager
       {
           // ...
-    +    private string $adminEmail;
 
           public function __construct(
               private MessageGenerator $messageGenerator,
               private MailerInterface $mailer,
-    +        private string $adminEmail
+    +         private string $adminEmail
           ) {
           }