[Bug]: Picker with help-text is not announced by screen readers

### Code of conduct

- [x] I agree to follow this project's code of conduct.

### Impacted component(s)

Picker

### Expected behavior

https://opensource.adobe.com/spectrum-web-components/components/picker/#use-help-text-to-show-context
The help-text should be announced by screen-readers and be able to both render and get an accessible association for help text with `sp-picker`

### Actual behavior

https://opensource.adobe.com/spectrum-web-components/components/picker/ (help text section at bottom)
This doesn’t work as the help text isn’t in the same shadow so the describedby can’t resolve

https://opensource.adobe.com/spectrum-web-components/components/help-text/#ensure-help-text-and-field-share-the-same-root
Despite it saying that sp-picker supports a help-text slot the sp-picker [documentation](https://opensource.adobe.com/spectrum-web-components/components/picker/api/) doesn’t agree

### Screenshots

_No response_

### What browsers are you seeing the problem in?

Microsoft Edge, Safari, Chrome, Firefox

### How can we reproduce this issue?

1. Go to https://opensource.adobe.com/spectrum-web-components/components/picker/#use-help-text-to-show-context
2. Open NVDA or JAWS screen readers
3. Check the help-text is not announced by screen reader

### Sample code or abstract reproduction which illustrates the problem

_No response_

### Severity

SEV 4

### Logs taken while reproducing problem

_No response_

Start with the Picker help-text documentation and the Help Text guidance on sharing the same root, then reproduce the issue with a screen reader using the linked Picker example. Done means help text is rendered, associated with sp-picker, and announced by screen readers, with the Picker API documentation matching the supported slot.

Written by the indexing model from the issue text.