Allow critical Banner variant to use `onDismiss`

### Description

Currently, the Banner component doesn't allow onDismiss to be used if the critical variant is used.

We would like to be able to use the onDismiss button when using the critical variant.

### Steps to reproduce

Add a Banner component and configure variant as `critical` and onDismiss as non null.

### Version

v37.9.1

### Browser

_No response_