update initialShipping retrieve props

[bastienlm]

In stepsDefinition you call <AddressAndShippingMethod... component with props

 initialShipping={{
            shippingMethod: props.checkoutState.shippingMethod,
            shippingAdditionalInfo: props.checkoutState.shippingAdditionalInfo,
          }}

So to retrieve this props on AddressAndShippingMethod, you need to simply retrieve it with props.initialShipping

The issue created: the shipping method selected by the user is not saved if you return to the shipping method select step after choosing one method.