kubeadm: Use the release-1.11 branch by default

[luxas]

What this PR does / why we need it:

Carries #63919

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes kubernetes/kubeadm#820

Special notes for your reviewer:

Release note:

kubeadm: Use the release-1.11 branch by default

cc @kubernetes/sig-cluster-lifecycle-pr-reviews @kubernetes/kubernetes-release-managers
/kind cleanup
/priority critical-urgent
/milestone v1.11
/status approved-for-milestone
/assign @timothysc

[k8s-github-robot]

[MILESTONENOTIFIER] Milestone Pull Request: Up-to-date for process

@luxas @timothysc

Pull Request Labels

• sig/cluster-lifecycle: Pull Request will be escalated to these SIGs if needed.
• priority/critical-urgent: Never automatically move pull request out of a release milestone; continually escalate to contributor and SIG through all available channels.
• kind/cleanup: Adding tests, refactoring, fixing old bugs.

Help

• Additional instructions
• Commands for setting labels

[timothysc]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: luxas, timothysc

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• cmd/kubeadm/OWNERS [luxas,timothysc]

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[luxas]

/retest

[timothysc]

/test pull-kubernetes-e2e-gce-100-performance

[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[k8s-github-robot]

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here.