Ship randomUUID in secure contexts

Remove feature flag from randomUUID

Refs: https://wicg.github.io/uuid/
Bug: 1197594
Change-Id: I62755566ae7a4f7c2b775f2e8a3ed10a20243d3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2881025
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Commit-Queue: Benjamin Coe <bencoe@google.com>
Cr-Commit-Position: refs/heads/master@{#882064}