Remove webhook builder when controller-runtime allows overriding a mutation handler

[alculquicondor]

What would you like to be cleaned:

Remove pkg/controller/jobframework/webhook/builder.go when kubernetes-sigs/controller-runtime#2932 is merged and released.

Why is this needed:

We duplicated the file to be able to provide a fix in Kueue faster in #3132

[alculquicondor]

Do not assign this issue yet, because #3132 is not merged yet.

[mimowo]

Closing in favor of #3469, as with the controller-runtime fix we can drop also our defaulter altogether.

[mimowo]

/close

[k8s-ci-robot]

@mimowo: Closing this issue.

In response to this:

/close

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