Remove deprecated DeliveryJob

lib/gitlab/marginalia/comment.rb

@@ -28,7 +28,7 @@ module Gitlab
         # We are using 'Marginalia::SidekiqInstrumentation' which does not support 'ActiveJob::Base'.
         # Gitlab also uses 'ActionMailer::MailDeliveryJob' which inherits from ActiveJob::Base.
         # So below condition is used to return metadata for such jobs.
-        if job.is_a?(ActionMailer::MailDeliveryJob) || job.is_a?(ActionMailer::DeliveryJob)
+        if job.is_a?(ActionMailer::MailDeliveryJob)
           {
             "class" => job.arguments.first,
             "jid"   => job.job_id