[fix] Accordion does not apply className to the Button under the Heading in AccordonItem

[KeithWaddell-REISys]

ReactUSWDS Version & USWDS Version:

USWDS 3.7.1
ReactUSWDS 9.0.0

Describe the bug

The AccordionItem componenent renders a Button underneath a Header. The Header applies the 'className' property, but the Button underneath does not. This results in being unable to style the Button, which is undesirable, as in my case I want to be able to style the Button so that it looks similar to the child content, for example matching the background color and text.

To Reproduce
Steps to reproduce the behavior:

Use the Accordion Component, style it with the 'className' property, observe the styling on the Button that is rendered

Expected behavior

The styles applied by the classes should also apply to the Button

Screenshots

Additional context

Device and Browser Information (please complete the following information if describing a UI bug):