lib: replace var w/ let

replace var w/ let in lib/internal/error-serdes.js

PR-URL: #30386
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/error-serdes.js

@@ -48,7 +48,7 @@ function TryGetAllProperties(object, target = object) {
 function GetConstructors(object) {
   const constructors = [];
 
-  for (var current = object;
+  for (let current = object;
     current !== null;
     current = Object.getPrototypeOf(current)) {
     const desc = Object.getOwnPropertyDescriptor(current, 'constructor');
@@ -82,7 +82,7 @@ function serializeError(error) {
     if (typeof error === 'object' &&
         ObjectPrototype.toString(error) === '[object Error]') {
       const constructors = GetConstructors(error);
-      for (var i = 0; i < constructors.length; i++) {
+      for (let i = 0; i < constructors.length; i++) {
         const name = GetName(constructors[i]);
         if (errorConstructorNames.has(name)) {
           const serialized = serialize({