doc: EKS end-of-life is not clear

For EKS releases, it's not clear what EOL means here. The documentation says:

> EOL refers to when an interim Ubuntu release (for example, Lunar Lobster 23.04) has reached end-of-life [and will no longer enjoy support](https://ubuntu.com/about/release-cycle/), or when EKS is [no longer supported by AWS](https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html).

The link to the kubernetes version and support lifecycle has `standard` and `extended` support. We should make it clear when our images are EOL (after `standard` or after `extended` support ends?)

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Document: aws-explanation/ec2-image-retention-policy.rst