chore: Upgrade supported Node.js to 20

[mshabarov]

Node.js goes out of support and React 19 needs Node.js 20+

[Artur-]

This seems to be a 24.0 list and now you are changing only one part of it but still linking to 24.0.0 release notes above. It should be made clearer that this is for the latest minor of Vaadin 24, link to that and also update all the other rows from 24.7.0 release notes

[peholmst]

Is this PR still relevant?

[mshabarov]

Yes, still relevant, Vaadin 24.7+ (latest supported minor versions) are all have Node.js 20 as a minimum supported. It was abandoned by me in favour of other tasks, but need still to figure out how this article is aligned with the release notes and how to address Artur's comment above.

[peholmst]

@mshabarov Understood. If you want this change to show up in the main branch as well (currently used for V25), add the target/main label to the PR. It will be automatically cherry-picked after merging.

[mshabarov]

Yes, I don't even remember why haven't I chosen the main branch from the beginning.

[peholmst]

@mshabarov Probably because the main branch was created yesterday 😄 .