Describe the problem
A clear and concise description of the problem. Which components are affected?

OCP uses variant="plain" in our NotificationBadge. This was approved by UX back during the PF6 upgrade, but this is an undocumented variant

How do you reproduce the problem?
Provide steps to reproduce. A codesandbox demonstrating the problem is appreciated.

Try using variant="plain" in NotificationBadge

Expected behavior
A clear and concise description of the expected behavior.

No type error and this type is documented

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

No. We use a @ts-expect-error now, added in openshift/console#15472

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

OCP 4.21 / 4.22