content: using "aria-labelledby", as suggested by the Accessibility Guidelines, never worked with modals

URL

https://ionic.io/docs/accessibility/ion-modal

Issue Description

In the Accessibility Guidelines for modals, it says:

In the above example the logical choice for an accessible name would be the ion-title of "Welcome". We can associate the modal with this by setting the aria-labelled attribute and giving the ion-title an id:

Leaving aside that it should be aria-labelledby, this has never worked as the only two attributes that are pushed down to the actual div that also gets assigned the role attribute of "dialog" are role and aria-label, as seen here in the code for modal.

So either the code needs a fix to support aria-labelledby, or the docs need to be adjusted.

Start with the accessibility guidance at https://ionic.io/docs/accessibility/ion-modal and the linked modal implementation at core/src/components/modal/modal.tsx around line 367. Verify the documented aria-labelledby behavior against the implementation; done means either supporting it in the modal or correcting the guide to describe the supported attribute.