Fix cardNumber type and update last4Digits assignment for correct slicing

Author: chefmatthaus-hub

Sprint-2/2-mandatory-errors/3.js

@@ -1,5 +1,5 @@
-const cardNumber = "4533787178994213";
-const last4Digits = cardNumber.slice(-4);
+const cardNumber = 4533787178994213;
+const last4Digits = String(cardNumber).slice(-4);
 
 // The last4Digits variable should store the last 4 digits of cardNumber
 // However, the code isn't working