fix: remove client-side validation from example guestbook operator

[ChristopherFry]

This pull request removes the client-side apply validation from the example guestbook operator allowing the operator to successfully reconcile changes.

Previously the operator would show this error when reconciling:

2023-10-22T21:39:20-07:00       ERROR   applying manifest       {"controller": "guestbook-controller", "object": {"name":"guestbook-sample","namespace":"default"}, "namespace": "default", "name": "guestbook-sample", "reconcileID": "1063a260-c92e-43ea-b82f-cf2114cdbeef", "error": "client-side validation is no longer supported"}

This error is due to client-side validation being deprecated in the direct applier with #352.

[k8s-ci-robot]

Hi @ChristopherFry. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ChristopherFry]

/cc @justinsb

[justinsb]

Thanks @ChristopherFry!

This reminds me of an idea that we've had but never written down, IIRC: we should log a warning when users use things/don't use things we recommend. Here it's pretty clear-cut and gives an obvious error, but it would still be better if that warning happened earlier. With an env-var, we could even switch it between warning or fatal or silent, corresponding to development vs production.

In any case...

/approve /lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ChristopherFry, justinsb

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