ARIA role "tab" not allowed for label element

[juthilo]

In the tab component, the label element gets the attribute role="tab".

According to the HTML spec (see label entry in table in linked section), no roles are allowed for the native label element, because it has "strong native semantics" and its role should not be overridden.

This gets flagged by our accessibility checker unless we explicitly disable the rule.

I saw that similar code was still included in db-ui/mono, so I hope we can find a solution for the current and future component that is fully compliant.