Remove some compat quirk

[petamoriken]

#1713 (comment)

types/web also has some compat quirk that had to mismatch with the spec, e.g. ChildNode being only a mixin interface inherited by some Node variants but types/web had to make it inherit from Node, reversing the inheritance, because back in the day we thought maybe we should put the compat first before correctness.

But if microsoft/TypeScript#58222 didn't break DefinitelyTyped then maybe it's a good chance to remove one quirk.

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @saschanaz - if they write a comment saying "LGTM" then it will be merged.

[saschanaz]

Oh I said the quirk #1713 is removing, not this quirk. I'm much less confident that this would be compatible with the ecosystem. But you can try submitting a draft PR into microsoft/TypeScript with this change and see what it catches.