[Mailer][Notifier] Simplify transport service registration + sorting

Author: OskarStark

Tests/Exception/UnsupportedSchemeExceptionTest.php

@@ -40,10 +40,10 @@ public static function setUpBeforeClass(): void
             BrevoTransportFactory::class => false,
             GmailTransportFactory::class => false,
             InfobipTransportFactory::class => false,
+            MailPaceTransportFactory::class => false,
             MailerSendTransportFactory::class => false,
             MailgunTransportFactory::class => false,
             MailjetTransportFactory::class => false,
-            MailPaceTransportFactory::class => false,
             MandrillTransportFactory::class => false,
             PostmarkTransportFactory::class => false,
             ScalewayTransportFactory::class => false,