Update create-guest-cart.md

the input type of mutation is wrong

src/pages/graphql/schema/cart/mutations/create-guest-cart.md

@@ -10,7 +10,7 @@ The `createGuestCart` mutation creates an empty shopping cart for a guest shoppe
 
 ```graphql
 mutation {
-  createGuestCart(input: ApplyCouponToCartInput) {
+  createGuestCart(input: CreateGuestCartInput) {
       CreateGuestCartOutput
   }
 }