[SPARK-49331][FOLLOWUP] Fix `cpu` to `cpus` in `setup-minikube` setting

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR is a follow-up of the following PR to fix cpu to cpus in setup-minikube setting.

• #82

Why are the changes needed?

This was a typo and CI complains like the following.

• https://github.com/apache/spark-kubernetes-operator/actions/runs/10503328332/job/29096477836

Warning: Unexpected input(s) 'cpu', valid inputs are ['start', 'cache', 'minikube-version', 'driver', 'container-runtime', 'kubernetes-version', 'cpus', 'memory', 'network-plugin', 'cni', 'addons', 'extra-config', 'feature-gates', 'listen-address', 'mount-path', 'install-path', 'wait', 'insecure-registry', 'start-args']

Does this PR introduce any user-facing change?

No, this is an infra bug fix.

How was this patch tested?

Manually check the CI logs.

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

cc @TQJADE

[dongjoon-hyun]

Thank you, @TQJADE .

[dongjoon-hyun]

For your Spark PR, I fixed it.

[dongjoon-hyun]

Could you review this PR, @viirya ?

[viirya]

Looks good to me.

[dongjoon-hyun]

Thank you! Merged to main.