Fix default-container announcement in 1.21 major themes

[lojies]

What type of PR is this?

/kind bug

What this PR does / why we need it:

kubectl cmd use the kubectl.kubernetes.io/default-container annotation for default container not label.

Which issue(s) this PR fixes:

Fixes #100961

Special notes for your reviewer:

Does this PR introduce a user-facing change?

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

[k8s-ci-robot]

Hi @lojies. 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.

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

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[wilsonehusin]

Thanks for submitting the PR! Would you mind to put NONE on the release note block? I will get to this before/after #100968, whichever goes green first.

/triage accepted
/ok-to-test
/remove-kind bug
/kind documentation
/priority important-soon

[wilsonehusin]

/retitle Fix default-container announcement in 1.21 major themes

[yangjunmyfm192085]

/lgtm

[yangjunmyfm192085]

/retest

[yangjunmyfm192085]

/release-note-none

[lojies]

/test pull-kubernetes-e2e-gce-ubuntu-containerd

[pacoxu]

/assign @feiskyer
for approval

[wilsonehusin]

/approve

thanks @lojies!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lojies, wilsonehusin

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

The pull request process is described here

Needs approval from an approver in each of these files:

• CHANGELOG/OWNERS [wilsonehusin]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

@lojies: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-kubernetes-e2e-kind	65f4fd8	link	/test pull-kubernetes-e2e-kind

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[wilsonehusin]

/retest