Fix 1.js: use let instead of const to allow reassignment

Author: lamlakamana-oss

Sprint-2/2-mandatory-errors/1.js

@@ -1,4 +1,10 @@
 // trying to create an age variable and then reassign the value by 1
 
-const age = 33;
+let age = 33;
 age = age + 1;
+
+// Error: TypeError: Assignment to constant variable. (at 1.js:4:5)
+// Cause: On line 4, the code is trying to change the value of `age`. However, 
+//        `age` was created using `const`, which means its value cannot be 
+//        changed after it has been assigned.
+// Fix: If the value of a variable needs to change later, use `let` instead of `const`.