Weekly self-test failed due to underlying Node version change

[ximon18]

See:

• https://github.com/NLnetLabs/ploutos-testing/actions/runs/9823032272/job/27201312704#step:3:21
• https://github.com/actions/checkout/issues/1809

[ximon18]

I've isolated and resolved the issue in testing branch 111-weekly-self-test-failed-due-to-underlying-node-version-change.

A ploutos-testing packaging run that succeeds when using this branch can be seen here: https://github.com/NLnetLabs/ploutos-testing/actions/runs/10091316883