add ubi8 and kubectl images to tests/images.txt

General MR

Summary

Adds images.txt to get the registry1.dso.mil/ironbank/redhat/ubi/ubi8-minimal:8.8 and registry1.dso.mil/ironbank/opensource/kubernetes/kubectl:1.27.5 images included in Kyverno's release images.txt (Summarize the purpose of the MR)

Related to big-bang/bigbang#1801 (closed)

Relevant logs/screenshots

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