Remove kubectl alpha debug command in 1.21

[pandaamanda]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

kubectl: The deprecated `kubectl alpha debug` command is removed. Use `kubectl debug` instead.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

@pandaamanda: This issue is currently awaiting triage.

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[k8s-ci-robot]

Hi @pandaamanda. Thanks for your PR.

I'm waiting for a kubernetes 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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[dougsland]

/ok-to-test
/lgtm

[pandaamanda]

/assign @brendandburns

[dougsland]

/cc @rikatz

[soltysh]

/approve
/hold
for @verb final word

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pandaamanda, soltysh

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• staging/src/k8s.io/kubectl/OWNERS [soltysh]

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[verb]

Thanks @pandaamanda !

/lgtm
/hold cancel