Bump CEL to v0.20.1

[bigkevmcd]

Changes

This registers the newest cel Extensions.

• Lists
• Sets
• Maths

The docs are updated and the cel-eval tool has been updated to register the extensions.

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• [X] Has Docs if any changes are user facing, including updates to minimum requirements e.g. Kubernetes version bumps
• [X] Has Tests included if any functionality added or changed
• [ ] Follows the commit message standard
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• [ ] Has a kind label. You can add one by adding a comment on this PR that contains /kind <type>. Valid types are bug, cleanup, design, documentation, feature, flake, misc, question, tep
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/kind cleanup

Release Notes

CEL interceptor updated to cel-go v0.20.1 and extensions for manipulating lists, sets and mathematical functions have been added.

[bigkevmcd]

@khrm Updated with the correct registrations.

[tekton-robot]

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[khrm]

@savitaashture Let's merge this for v0.27.0