Remove K8s v1.27.x from the `techprev_versions` list and allow its deployment without ` --allow-preview-versions` flag

Created by: matofeder

As a KaaS administrator, I want to deploy the latest stable version of K8s which is also supported by the latest stable version of CAPO. Currently, this K8s version is v1.27.x.

Remove v1.27.x from the techprev_versions list and allow deployment of v1.27.x without any special flag like --allow-preview-versions. Currently, it is easily possible because:

• Kubernetes v1.27.x is offically supported by cluster-api-provider-openstack since v1alpha6 (v0.7).

• Cluster-api-provider-openstack version in SCS/k8s-cluster-api-provider has been bumped to v0.7.3 #427