docs: add containerd command to restart nginx-proxy

[nicolas-goudry]

What type of PR is this?

/kind documentation

What this PR does / why we need it:

When using containerd as container engine, the command to restart nginx-proxy after adding a control plane node is invalid as it uses docker.

Which issue(s) this PR fixes:

Fixes #10404

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Document containerd command to restart nginx-proxy container when adding control plane node

[k8s-ci-robot]

Hi @nicolas-goudry. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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[mzaian]

Thanks @nicolas-goudry

/lgtm
/ok-to-test

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mzaian, nicolas-goudry

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