Use 2.426.1 in lts profile instead of 2.414.3

[MarkEWaite]

Use 2.426.1 in lts profile instead of 2.414.3

Jenkins 2.426.1 has been released and is being used on ci.jenkins.io and in many other configurations. Let's use it for acceptance testing as well.

Testing done

Rely on ci.jenkins.io to do the testing. 2.426.1 pre-release testing with ATH was successful.

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6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[basil]

Thanks for the PR!