Improve convert-runbook script to work with yq >= v4.x

[mfranczy]

Currently we are out of sync with yq version for hack/prepare-release.sh (req yq >= v4.x) and hack/convert-runbook.sh (req yq == v3.4). Additionaly we should update the README https://github.com/kubermatic/docs/blob/master/hack/README.md

[kubermatic-bot]

Issues go stale after 90d of inactivity. After a furter 30 days, they will turn rotten. Mark the issue as fresh with /remove-lifecycle stale.

If this issue is safe to close now please do so with /close.

/lifecycle stale

[kubermatic-bot]

Stale issues rot after 30d of inactivity. Mark the issue as fresh with /remove-lifecycle rotten. Rotten issues close after an additional 30d of inactivity.

If this issue is safe to close now please do so with /close.

/lifecycle rotten

[kubermatic-bot]

Rotten issues close after 30d of inactivity. Reopen the issue with /reopen. Mark the issue as fresh with /remove-lifecycle rotten.

/close

[kubermatic-bot]

@kubermatic-bot: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity. Reopen the issue with /reopen. Mark the issue as fresh with /remove-lifecycle rotten.

/close

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