Remove branch job for 1.23

[cici37]

What should be cleaned up or changed:
The branch job for 1.23 should be removed since 1.23 is EOL:
#29172 (comment)

Provide any links for context:
It would be a followup work on: #29172

/sig release
/assign @ramrodo

[BenTheElder]

Partially done in #29387 ? cc @xmudrii @jeremyrickard

[xmudrii]

@BenTheElder I think that it should be completely done. Is there anything else that should be removed?

[ramrodo]

I think this issue is completely done now

[justaugustus]

Closed via #29387.
/close

[k8s-ci-robot]

@justaugustus: Closing this issue.

In response to this:

Closed via #29387.
/close

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