switch to gopkg.in/yaml.v3

[BenTheElder]

https://github.com/kubernetes/test-infra/pull/33958/files#r1886682875

/priority backlog

we may also have to update dependency repos like sigs.k8s.io/prow

[BenTheElder]

/sig testing

[mkumatag]

/assign

[BenTheElder]

(#33979 (comment))

[mkumatag]

This is because of the following reason

$ go mod why -m gopkg.in/yaml.v3
# gopkg.in/yaml.v3
k8s.io/test-infra/experiment/coverage
github.com/go-openapi/spec    <====== (1)
github.com/go-openapi/swag
gopkg.in/yaml.v3

$ go mod why -m gopkg.in/yaml.v2
# gopkg.in/yaml.v2
k8s.io/test-infra/config/tests/mergelists
k8s.io/test-infra/config/tests/mergelists.test
github.com/GoogleCloudPlatform/testgrid/pkg/merger <====== (2)
gopkg.in/yaml.v2

(1) and (2) are imported modules that use these indirect dependencies. They are outside of the Kubernetes project, and we have minimal control over them.

[BenTheElder]

Testgrid is us and can be patched cc @michelle192837

(1) I'm less sure about. cc @pohly @jpbetz