NVDA reads top of page when hiding "dialog" content and focusing elsewhere

[zepumph]

From https://github.com/phetsims/gravity-force-lab/issues/234, we should submit a but report to NVDA to see if their logic can be improved.

```html

First Container

This is one container

Show second container

Second Container

This is a second container

Show first container

This snippet will likely be helpful. ```