[12.x] Update config/mail.php to match the latest core configuration (#6594)

* Update config/mail.php to match the latest core configuration

* Update mail.php

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

config/mail.php

@@ -85,6 +85,7 @@ return [
                 'smtp',
                 'log',
             ],
+            'retry_after' => 60,
         ],
 
         'roundrobin' => [
@@ -93,6 +94,7 @@ return [
                 'ses',
                 'postmark',
             ],
+            'retry_after' => 60,
         ],
 
     ],