Update Jenkins repository key URLs.

[nuclearsandwich]

Description

The repository signing keys for the Jenkins apt and rpm repositories have been rotated and the new signing keys are available at a separate URL from the previous ones.

As of 2023-06-19 the previous keys are no longer available and the URLs used prior to this patch 404 so I do not think there is an advantage to making this change conditional.

Background on the Jenkins repository change is here: https://www.jenkins.io/blog/2023/03/27/repository-signing-keys-changing/

Check List

• [x] A summary of changes made is included in the CHANGELOG under ## Unreleased
• New functionality includes testing.
• New functionality has been documented in the README if applicable.

[nuclearsandwich]

CI blocked re-running integration tests because of broken links to tickets.chef.io in the changelog (although these links were added in much earlier entries).

I don't think that it makes sense to disable link checking completely or to allow the markdown check to fail every time the changelog is touched. Can we ignore those specific urls somehow?

It seems like the markdown-link-check supports a json config file but I don't know if adding one here would be properly plumbed through the lint-unit workflow without making changes there. https://github.com/sous-chefs/.github/blob/main/.github/workflows/lint-unit.yml

[ramereth]

@nuclearsandwich broken links should be fixed or just removed. I have been removing those links in other CHANGELOG's too and I think the same should be the case here.

[nuclearsandwich]

Thanks for the feedback! Changelog fixes proposed in https://github.com/sous-chefs/jenkins/pull/809 after which I'll rebase this to include those changes.

[kitchen-porter]

Released as: 9.5.19