The barrier is currently not thread-safe but may be executed via
concurrent Sparkplug compilation. Remove the actual barrier code as
the remembered set is anyways not used yet.

Bug: v8:13018, chromium:1336850, chromium:1333414
Change-Id: I9287516d559cc3b10d170fa0fda36b26ca487a15
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3734809
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81438}