Comment 1 for bug 1887660

On discussion with senior collegues:-

If there is a problem pushing manifests for now we might just turn that off, manifests are only needed for ppc64le containers tagged but they aren't available so its safe to have them off.

* Came to know that pushing manifests is already off in master/usurri branch

https://github.com/rdo-infra/ci-config/blob/master/ci-scripts/dlrnapi_promoter/config/CentOS-8/master.ini#L11
https://github.com/rdo-infra/ci-config/blob/master/ci-scripts/dlrnapi_promoter/config/CentOS-8/ussuri.ini#L11

Proposed: https://review.rdoproject.org/r/#/c/28540/