Fix the code incorrctly exposed Intl["SegmentIterator"] that caused
Unreachable code in builtins-internal.cc

Bug: chromium:900013
Change-Id: I50d457a9f065d597b3bbb77a7a45011335c959da
Reviewed-on: https://chromium-review.googlesource.com/c/1306906Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57140}