config: add warning about new-stock ender 3s

[BluCobalt]

My Ender 3 (bought in 2021?) came with a 4.2.2 board out of the box. I just want to add this note to hopefully help someone else, because I lost a good couple of hours trying to figure this out ;)

[JamesH1978]

Thank you for submitting a PR, please be aware that you need to sign off to accept the developer certificate of origin, please see point 3 in https://github.com/Klipper3d/klipper/blob/master/docs/CONTRIBUTING.md#what-to-expect-in-a-review

Thanks James

[BluCobalt]

Should be good now.

[JamesH1978]

Thanks, looks fine to me as an informational, as this is indeed the case. The other option would be to create a whole new file referencing the date these started shipping without the melzi boards, but I think that could get confusing. @KevinOConnor what do you think?

Thanks James

[BluCobalt]

Actually, that might make more sense. A little bit of research says that this hardware change happened in July of 2020. Let me make that new config.

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