This was put in place because of #1798 (and PR #2102)

The state root event is emitted whenever the collapse is updated (in the updated hook) to ensure the collapse class persists on the toggle button due to component updating.

the bv::collapse::state event was really meant to be an internal only event for updating the state of the toggle button(s), but unfortunately made it's way into the documentation.

We might be able to find a better way of persisting the collapsed class in the v-b-toggle directive.