Chromium has rolled the Fuchsia SDK, so this can be removed now, and
the new zx_, etc. names used exclusively.

Bug: chromium:765754
Change-Id: I8bd60239da7a05e62d3b8d5209e1cfe898d8052a
Reviewed-on: https://chromium-review.googlesource.com/671769Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48071}