Downloads button warning no longer announced on Orca

When the downloads toolbar is clicked, the download warning message should be announced. Orca no longer seems to do this (my current version 46.1). Same problem in both Tor Browser 13.0 and 13.5. It still works as expected in the places.xhtml and about:downloads, and works fine on windows with NVDA.

This could be an issue for Orca to address. We might be able to hack around it.