As Istio's ambient mode will be GA in version 3.2 of OSSM, we should remove the big technology preview call out in the documentation: https://docs.redhat.com/en/documentation/red_hat_openshift_service_mesh/3.1/html/installing/ossm-istio-ambient-mode

This should only be done for the 3.2 release, as the banner should remain for the 3.1 docs.