Remove K8s v1.27.x from the techprev_versions list

Created by: matofeder

This PR removes K8s v1.27.x from the techprev_versions list and allows its deployment without --allow-preview-versions flag

/tested

• k8s v1.27.3 deployed without any allow-preview-versions warnings/errors if variable kubernetes_version = "v1.27.x" was set
• sonobuoy check-conformance passed

Closes #450 (closed)