GraphQL: Deprecate ShippingCartAddress.cart_items in favor of cart_items_v2 (#5949)

* update attributes and example

* Rewrite sentence

Author: keharper

guides/v2.3/graphql/mutations/set-shipping-address.md

@@ -92,7 +92,7 @@ The top-level `SetShippingAddressesOnCartInput` object is listed first. All chil
 Attribute |  Data Type | Description
 --- | --- | ---
 `cart_id` | String! | The unique ID that identifies the customer's cart
-`billing_address` | [ShippingAddressInput!](#ShippingAddressInput) | The billing address for a specific cart
+`shipping_addresses` | [ShippingAddressInput!](#ShippingAddressInput) | The shipping address for a specific cart
 
 ### CartAddressInput object {#CartAddressInputShip}