Drop v1.25.0 API testdata

[SataQiu]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Drop v1.25.0 API testdata.
Followup #117537

https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/api/testdata#populating-data-for-each-release

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[SataQiu]

/sig testing

[SataQiu]

/assign @liggitt

[pacoxu]

/lgtm
/priority important-soon
/triage accepted

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: c08b3ecc5157e34c491c39e3581132d4f1644ff1

[liggitt]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liggitt, SataQiu

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[humblec]

@liggitt / @pacoxu just to understand, why we keep only 2 version's data of serialization? I see every N release will have N-1 and N-2 data. don't we need the data of N-3 too?

[liggitt]

Currently, API servers only support one version of skew, so two historical versions (plus HEAD) is sufficient.

If we expanded API server skew in the future (for example, as part of skip-level upgrade support), we would need to include more historical data.

[pacoxu]

You can refer to https://kubernetes.io/releases/version-skew-policy/#kube-apiserver for skew policies.