[mjsunit] Dont generate dumps from regression test

The --perf-prof flag generates unwanted .dump files, while the
--perf-prof-unwinding-info flag enables the functionality under test here.

R=jgruber@chromium.org
BUG=chromium:913844

Change-Id: Ie5ee374977d6105854f42065600dac1bc5ba6df7
Reviewed-on: https://chromium-review.googlesource.com/c/1409363
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58791}

test/mjsunit/regress/regress-913844.js

@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --disable-in-process-stack-traces --perf-prof --turbo-loop-rotation
+// Flags: --disable-in-process-stack-traces --perf-prof-unwinding-info --turbo-loop-rotation
 for (var x = 0; x < 1000000; x++)
 ;