Fix for Accordion accessibility issue

[ldoliv]

What does this PR do?

Fixes the accessibility violation "Ensure landmarks are unique" that can be seen in the storybook accessibility tab.

Where should the reviewer start?

Any story under the Accordion component

What testing has been done on this PR?

Was run before commiting: yarn test-update yarn test

How should this be manually tested?

Check the accessibility tab for any Accordion component story

Do Jest tests follow these best practices?

• [ ] screen is used for querying.
• [ ] The correct query is used. (Refer to this list of queries)
• [ ] asFragment() is used for snapshot testing.

Any background context you want to provide?

What are the relevant issues?

https://github.com/grommet/grommet/issues/6124

Screenshots (if appropriate)

Before:

After:

Do the grommet docs need to be updated?

No

Should this PR be mentioned in the release notes?

No

Is this change backwards compatible or is it a breaking change?

[ldoliv]

Updated the branch