Revert "Collect user opt-in before enabling account-storage for passwords"

This reverts commit c3c374663b69924fee30dec66c36bf1a2397d3cd.

Reason for revert: canary top crasher; see https://crbug.com/1029631.

Original change's description:
> Collect user opt-in before enabling account-storage for passwords
>
> This CL adds a pref that stores which accounts have opted in to use the
> Google account storage for passwords. While this pref is false,
> passwords can not be saved to the account, and passwords in the account
> are not downloaded.
> It also adds an entry to the password autofill dropdown that lets the
> user set the opt-in.
>
> Bug: 1024332
> Change-Id: Iac552c310d0e9f19ee2bb1893e217e60b1114d31
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1645294
> Commit-Queue: Marc Treib <treib@chromium.org>
> Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
> Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
> Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#720206}

TBR=sdefresne@chromium.org,treib@chromium.org,dvadym@chromium.org,jzw@chromium.org,mamir@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1024332,1029631
Change-Id: Ib859957d27a898652e001515652cde25a30ed1b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944497
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720424}