Remove aria-expanded from radios with conditional content when JS is enabled

[ttbarnes]

This PR removes the aria-expanded attribute from radios with conditional content.

Without this change, accessibility tools such as AXE and Lighthouse flag a critical issue:

ARIA attribute is not allowed: aria-expanded="false"

Currently, aria-expanded is not supported for radio buttons. This may change: w3c/aria#1404

[querkmachine]

Hi @ttbarnes, thanks for the contribution.

We currently don't intend to remove aria-expanded from conditional reveals as—despite being an invalid use under the the current ARIA specification—we've found that some screen readers do expose this information to users, and we haven't noticed any detrimental affects from the attributes being present.

In this instance, we believe the benefit to screen reader users outweighs being invalid according to the spec and, as you note, the spec may change in future to accommodate how we're using it.

Further information about our research and testing is in #979. The validation error in Axe is also listed as a known issue.

[ttbarnes]

Thank you @querkmachine - makes sense, closing this PR 👍