[test] Disable stress-bytecode-flush on mjsunit/regress/regress-786784

Temporarily disable stress-bytecode-flush on
mjsunit/regress/regress-786784 while we investigate failures related
to bytecode flushing.

Bug: v8:10560
Change-Id: Ieb5cc7ba87da04133e98c6be25c9a499d79543e0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2218038Reviewed-by: Marja Hölttä <marja@chromium.org>
Auto-Submit: Mythri Alle <mythria@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68046}

test/mjsunit/regress/regress-786784.js

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// TODO(mythria): Investigate why this is failing with stress-flush-bytecode and
+// remove the --no-stress-flush-bytecode here.
+// Flags: --allow-natives-syntax --no-stress-flush-bytecode
 
 function f() {
   function g(arg) { return arg; }