Bug - AlertGroup - li elements never unmount for timedout alerts

Describe the problem
When Alerts with a timeout are rendered inside an AlertGroup, the wrapper li element for the Alerts never unmounts when the Alerts do. This causes empty li elements to remain in the DOM.

How do you reproduce the problem?
Go to the alert timeout example and add an alert in the example. Inspect the DOM and notice that when the Alert itself unmounts, the wrapper li element remains with nothing inside of it. Add another Alert and notice that the empty li still remains in addition to a new li with the new Alert rendered inside of it.

Expected behavior
The li elements would unmount the same as the Alerts themselves

Is this issue blocking you?
List the workaround if there is one.

Screenshots
If applicable, add screenshots to help explain the issue.

What is your environment?

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

What is your product and what release date are you targeting?

Any other information?

Start with the AlertGroup component and reproduce the issue using the alert timeout example. Inspect the DOM as timed-out Alerts disappear and trace how their wrapper li elements are rendered and removed. Done means timed-out Alerts no longer leave empty li elements, including when another Alert is added.