Newsletter: Pre-publish panel focussing on Newsletter component on Gutenberg trunk

### Issue

Ordinarily when creating a post and clicking publish, I see that it is expected that the Newsletter component in the pre-publish panel expands (aria-expanded is set to true).

When testing with the Gutenberg Nightly plugin installed (Gutenberg trunk), if the Newsletter component was out of site initially then it will be brought in focus with the scroll moving down.

The reason this could be an issue is that the final 'publish' button is now out of site. This did cause me some confusion initially, so inevitably would do for others (though only on small screens) - once those changes (and if those changes) make their way into core.

### To replicate

- On a site with the latest stable Jetpack version (or trunk), install the Gutenberg Nightly plugin
- Create a new post, and ensure the screen height is reasonably small (around 600px for example)
- When clicking publish, notice that the Newsletter component becomes visible, hiding the final 'Publish' button.
- If you have subscriptions enabled (the above assumes the default, disabled), it appears that both the Access and Newsletter panels are auto-expanded and brought into focus.

### What I'd expect to see

I would expect that even if the Newsletter panel is expanded, I'd still be able to see the Publish button

No source file or test is named. Reproduce the publish flow with Gutenberg Nightly on a short viewport, checking the Newsletter and Access panels and the final Publish button; done means expanding the Newsletter panel does not hide the Publish button.

Written by the indexing model from the issue text.