Remove useless aria roles

[avetisk]

As per standard definition/recommendation, elements such as <button> or <th> should not have role attribute which are already implicitly defined.

https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/columnheader_role#best_practices

[gpbl]

Thanks for the suggestion @avetisk. I agree to remove them! We should confirm first that VoiceOver reads them correctly: it should - but better double check.