[bug-bash] README and setup-gcp conflicts on Kubernetes beta APIs enablement #3233

Steps to reproduce

Read README.md and tools/setup-gcp/README.md#2-create-cluster.

Expected

The two docs agree.

Actual

• README.md tells bring-your-own-cluster users that the required beta APIs "can only be enabled at cluster creation".

• setup-gcp section says GKE 1.37 and higher serve the APIs under v1 by default. A 1.36 cluster "can be fixed in place".