[Announce] VoiceOver announces incomplete changes in some situations

[chaance]

Per #133 (comment):

Seems to work pretty well although didn't announce the full sentence in Safari + Voiceover

The closest issue we could find elsewhere suggests this is a Safari bug. https://core.trac.wordpress.org/ticket/36853

I tried implementing a similar empty string fix suggested in the WordPress bug, but that doesn't work as intended in NVDA when working with stacked notifications (as a toast likely will). This may be something we can do separately in a Status package where notifications are replaced completely instead of stacked, as that it primarily where the problem lies and is most likely to occur.

Referenced in #166

[benoitgrelard]

This primitive will be deprecated soon as it doesn't fit with our high-level use case approach.