chore: fix a non working example in README.md

[faridevnz]

The current version of the example fails with:

throw new InvalidTransitionCondition("State must have valid transition condition (autoTransition or transitionGuard) if not final");

[marco-ippolito]

I think the error itself is wrong.
A state if not final should have either autoTransition or transitionTo.
transitionGuard should always be optional