Add sig labels to markdown

[npolshakova]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Slack discussion: https://kubernetes.slack.com/archives/CN1KH4K9A/p1721224163843589

Which issue(s) this PR fixes:

When the map file text is replaced, the resulting markdown does not include the SIG labels. See an example of this where the old release notes have the sig labels removed.

You can reproduce this by running with the latest krel:

go run ./cmd/krel release-notes --create-draft-pr --fork=npolshakova --fix --tag  v1.31.0-alpha.3 --list-v2 --log-level trace --repo=/Users/ninapolshakova/kubernetes/kubernetes

Special notes for your reviewer:

None

Does this PR introduce a user-facing change?

Edited release notes by the release notes team will now have the sig labels included at the end of the markdown.

[saschagrunert]

Just a nit. @npolshakova thank you for approaching a fix! Can you verify if that works for you?

[npolshakova]

Just a nit. @npolshakova thank you for approaching a fix! Can you verify if that works for you?

Yep, the unit test confirmed it but I also re-ran krel to sanity check the sig labels are now being added and none of the sig labels are removed: https://github.com/kubernetes/sig-release/pull/2570/files#r1683006327

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: npolshakova, saschagrunert

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