KEP-1326L Update 3rd party docs content KEP

[lmktfy]

• One-line PR description: Tidying for existing KEP

• Issue link: Doc policies for third party content #1326

• Other comments:

  This is a cut down version of the change I proposed in KEP-1326: update KEP and mark implemented #5245
  This PR does not mark the KEP as implemented (it remains provisional and unapproved).

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[k8s-ci-robot]

PR needs rebase.

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