Update deployKF "Target Platform" to "Multiple"

[thesuperzapper]

DO NOT MERGE until #3842 is merged.

We are trying to reduce confusion for users who are trying to figure out which distributions support their Kubernetes clusters.

This PR makes the following changes:

• Rewords "All Certified Kubernetes Distributions" to "Multiple"
  • I have only updated deployKF, if other distributions want, they can copy this in their own PRs.
  • Also adds a [list] reference, which links to that distribution's list of supported Kubernetes platforms.
• Makes the [version matrix] and [release notes] references lowercase (makes it less busy on screen)

Old Screenshot

New Screenshot

[google-oss-prow]

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[google-oss-prow]

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