chore(channels): bump k8s and ubuntu ami versions in alpha channel

[moshevayner]

What this PR does / why we need it:
Update k8s versions and Ubuntu AMI versions (focal/jammy) to latest

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

Special notes for your reviewer:

• https://github.com/kubernetes/kubernetes/releases/tag/v1.28.5
• https://github.com/kubernetes/kubernetes/releases/tag/v1.27.9
• https://github.com/kubernetes/kubernetes/releases/tag/v1.26.12
• https://cloud-images.ubuntu.com/locator/ec2/ (use search bar to lookup focal and jammy)

/cc @hakman

[hakman]

Very nice and much appreciated. Thanks @moshevayner!
/lgtm
/approve

[k8s-ci-robot]

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