Earlier quoted context omitted.
You should still be able to use alt="" to indicate that it is "decorative" and not meaningful imagery for a visually-impaired user.
Instead use the ARIA tag role="presentation": https://developer.mozilla.org/en-US/docs/Web/Accessibility/A... to indicate when an element has no semantic meaning and is purely visual.
That said, the use of empty alt tags is generally discouraged and not even allowed together with the ARIA presentation role in most cases.
This decision of theirs will steer developers towards non-compliant/asemantic code. It's really stupid.
https://html.spec.whatwg.org/multipage/images.html#alt