Drive-by: add unscopable test for Array.prototype.toReversed.

Bug: v8:12764
Change-Id: I9d7dd8d4eae6d23811382b6795c2c6ff7f76be72
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717552Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81364}