util: replace var with let

PR-URL: #30439
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/util/comparisons.js

@@ -59,7 +59,7 @@ function areSimilarFloatArrays(a, b) {
   if (a.byteLength !== b.byteLength) {
     return false;
   }
-  for (var offset = 0; offset < a.byteLength; offset++) {
+  for (let offset = 0; offset < a.byteLength; offset++) {
     if (a[offset] !== b[offset]) {
       return false;
     }