benchmark: fix webstream pipe-to

PR-URL: https://github.com/nodejs/node/pull/49552
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

benchmark/webstreams/pipe-to.js

@@ -18,7 +18,7 @@ async function main({ n, highWaterMarkR, highWaterMarkW }) {
   const rs = new ReadableStream({
     highWaterMark: highWaterMarkR,
     pull: function(controller) {
-      if (i++ === n) {
+      if (i++ < n) {
         controller.enqueue(b);
       } else {
         controller.close();