[3.5] Bump Go version to 1.21.11: CVE 2024-24790 fix

[ArkaSaha30]

This PR bumps the Go version to go1.21.11 due to CVE-2024-24790/ GO-2024-2887.

Issue link: #18127

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[k8s-ci-robot]

Hi @ArkaSaha30. Thanks for your PR.

I'm waiting for a etcd-io 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[henrybear327]

/ok-to-test

[ahrtr]

LGTM

Thanks @ArkaSaha30

[ivanvc]

/retitle [3.5] Bump Go version to 1.21.11: CVE 2024-24790 fix