Update cart-shipping.php

When a customer from a country which does not have a required state (e.g. Netherlands/UK) and tries to complete checkout without entering a state, WooCommerce currently gives the customer this error "Please fill in your details to see available shipping methods." I have made a change to check whether the state/postocde are required before giving this error message.

I have also changed "There doesn't seem to be any available shipping methods" to "There don't seem to be any available shipping methods".