[test] Disable promise error handling for benchmark

This slows down promise benchmarks since we process all unhandled promises.

Bug: vu:1099632
Change-Id: I2188a2842ec0a69ca93e5d406f10371ceff60f9b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2270235Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68575}

test/js-perf-test/AsyncAwait/baseline-naive-promises.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 new BenchmarkSuite('BaselineNaivePromises', [1000], [
   new Benchmark('Basic', false, false, 0, Basic, Setup),