Remove katello:migrate_deb_content_attributes_to_pulp3 from foreman-rake

Since theforeman/foreman-documentation#5082 we
no longer need to allow this action in foreman-rake.

Author: ShimShtein

src/roles/foreman/templates/foreman-rake.j2

@@ -15,7 +15,6 @@ validate_actions() {
         "foreman_tasks:cleanup"
         "interfaces:clean"
         "katello:delete_orphaned_content"
-        "katello:migrate_deb_content_attributes_to_pulp3"
         "katello:upgrade_check"
         "ldap:refresh_usergroups"
         "orchestration:dhcp:add_missing"