Removes new_target member and getter since none of the Array builtins in
builtins-array-gen.* use it (since none of them are constructors).

delete new_target getter and member variable

Bug: v8:7570
Change-Id: Ia23af014750278d64447bb58171955d909fdb5a8
Reviewed-on: https://chromium-review.googlesource.com/1032556Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52845}