kubeadm: amend constant to kubelet.

[calvin0327]

What type of PR is this?

/kind bug

What this PR does / why we need it:

There is existing constant for kubelet.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

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

[neolit123]

this looks fine, thanks

/lgtm
/approve
/triage accepted

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: calvin0327, neolit123

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