🌱 enable errorlint and unused linters

[xrstf]

This PR enables another 2 linters and fixes the issues that they brought up.

/kind cleanup

[k8s-ci-robot]

Hi @xrstf. 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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[alvaroaleman]

/ok-to-test

[alvaroaleman]

/retest

[alvaroaleman]

thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alvaroaleman, xrstf

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