Previously, if the new length was less than the current length, we ignored
the "configurable" value and set the length as requested. We already threw
if the new length was greater than or equal to the current length.

New behavior matches the spec and other implementations.

Bug: v8:9460
Change-Id: Idb92fd121bdaa707f6abd2d2082628bbf3541b83
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1709336Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62855}