:bug: Use the GKE production API instead of beta

[cardil]

Which issue(s) this PR fixes:
Fixes https://github.com/knative-sandbox/kn-plugin-event/issues/242

What this PR does, why we need it:

This PR uses the default of production GKE API instead of beta.

[cardil]

/assign @dprotaso /assign @upodroid /assign @kvmware /cc @mgencur

[dprotaso]

/lgtm /approve

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cardil, dprotaso, upodroid

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[upodroid]

btw, there is no functional difference between GA and beta APIs for GA features. The underlying feature is GA so it shouldn't be causing problems.

Have you read this guide from Google? https://cloud.google.com/kubernetes-engine/docs/how-to/nodelocal-dns-cache#known_issues

[cardil]

@upodroid See https://github.com/knative-sandbox/kn-plugin-event/issues/242#issuecomment-1322745383 and Slack thread: https://knative.slack.com/archives/CA9RHBGJX/p1668770983220909

[cardil]

Fixes https://github.com/knative-sandbox/kn-plugin-event/issues/242