Although the RC, EC, Z-stream image are supposed to be signed, our rebase procedure regularly uses nightly releases which may not contain signed images.
For this reason, we cannot have image signatures checking in 4.18 CI.

We cannot also rebase only on candidates, because the point of the rebase in our repository is to catch problems before they happen in ART. By trying to rebase only on candidates we'd be behind - we'd see errors that already happened for ART.

Discovered in rebase PR: https://github.com/openshift/microshift/pull/4442 

4.18 nightly

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