Revert "UI Notification for Gnubby U2F UI."

This reverts commit d95be619b5a98a02570063dfbb1c9c78ff54c2d4.

Reason for revert: New test fails on cros test bots, rel and dbg:
https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg/12442
https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-rel/24516

Original change's description:
> UI Notification for Gnubby U2F UI.
> 
> Bug: 757077
> Change-Id: I54305669b9fbbcb9191c814790ebe29a7dff0d62
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1404060
> Commit-Queue: Yulun Wu <yulunwu@chromium.org>
> Reviewed-by: Alexander Alekseev <alemate@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#661147}

TBR=alemate@chromium.org,apronin@chromium.org,yulunwu@chromium.org

Change-Id: Ibb4a66731dd358844c271117cf7a37565cc3643b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 757077
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1619063
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661199}
17 files changed