Increase old space size for regress-678917.js

When --always-promote-young-mc is enabled, this test becomes more
flaky. Increase old space size, such that objects fit into the
old generation during mark-compact.

Bug: v8:9192
Change-Id: Iad3b914c7d5b7bafa752f3b6178684a137bd8dad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1890101Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64830}

test/mjsunit/regress/regress-678917.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --max-old-space-size=1600 --nostress-incremental-marking
+// Flags: --max-old-space-size=2000 --nostress-incremental-marking
 
 // This test uses a lot of memory and fails with flaky OOM when run
 // with --stress-incremental-marking on TSAN.