About Modal: Refactor to be built with the modal component

[nicolethoen]

Follow up to patternfly/patternfly#4526

Per https://github.com/patternfly/patternfly/pull/5216/files, the .pf-c-about-modal-box component is no longer styled as its own modal, and is now a regular element/box. This update allows us to place the about modal component in the existing modal component. This is similar to how a wizard behaves when inside of a modal.

The update from core is to remove the following attributes from the about modal, since they will now be on the modal component

• role="dialog"
• aria-modal="true"
• aria-label[ledby]
• aria-describedby

We're using a large modal in the core demo, but I imagine that can be configurable by the user, similar to the existing wizard in a modal. Though I think it begs the question - if it's more composable to be used with the <Modal> (instead of shipping with the <Modal>):

• Should it be called <AboutModal>? Or should we take "modal" out of the name?
• Could it be used outside of a <Modal>?

cc @mcarrano @mceledonia @tlabaj - opinions on the usage/naming above?