Validator tests for removing "aria-expanded" from listbox support attributes

[spectranaut]

See: https://github.com/w3c/aria/pull/1862

This still needs issues on validators, although VNU doesn't seem to flag aria attributes used on roles that do not explicitly support them.

For example, the following does not error:

<div role="heading" aria-expanded=true>
  I'm a heading
</div>