remove validate-rhsa

[Ximinhan]

The http://sfm2.prodsec.redhat.com/ server is no longer operational, we can't use it anymore and their service move to a place where only errata can access, so deprecate this step for now.

https://redhat-internal.slack.com/archives/GDBRP5YJH/p1707370865294469

[openshift-ci[bot]]

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[openshift-merge-robot]

PR needs rebase.

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