Apply fixes from StyleCI

Author: ahinkle

src/Api/GuestCarts.php

@@ -173,8 +173,8 @@ public function removeCoupons($cartId)
      * Assign a specified customer to a specified shopping cart.
      *
      * @param  string   $cartId
-     * @param  integer  $customerId
-     * @param  integer  $storeId
+     * @param  int  $customerId
+     * @param  int  $storeId
      * @return array
      */
     public function assignCustomer($cartId, $customerId, $storeId)

tests/Api/GuestCartsTest.php

@@ -156,7 +156,7 @@ public function test_can_edit_item()
 
         $this->assertTrue($api->ok());
     }
-    
+
     public function test_it_can_assign_customer()
     {
         Http::fake([