[core] replace gopkg.in/yaml.v2 with sigs.k8s.io/yaml

[kayrus]

What this PR does / why we need it:

Fixes go list -m all and replaces outdated gopkg.in/yaml.v2 with sigs.k8s.io/yaml

Special notes for reviewers:

Release note:

NONE

[k8s-ci-robot]

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[k8s-ci-robot]

@kayrus: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cloud-provider-openstack-test	ff625cb	link	true	/test pull-cloud-provider-openstack-test

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.

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