Remove some compat quirk

[petamoriken]

https://github.com/microsoft/TypeScript-DOM-lib-generator/pull/1713#issuecomment-2248890913

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 https://github.com/microsoft/TypeScript/pull/58222 didn't break DefinitelyTyped then maybe it's a good chance to remove one quirk.