The property kInObjectPropertiesStartOrConstructorFunctionIndexOffset
was set as relaxed due to races with the layout_descriptor
(https://chromium-review.googlesource.com/c/v8/v8/+/555210/). The
layout_descriptor was removed with the removal of double field unboxing.

We are able to turn those property's accessors into non-atomic ones
since they are set at construction time.

Bug: v8:7790
Change-Id: I25c53f0e00718cca72ba86f8475af9ecefb7ba3d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2843359
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74174}