Revert "Add dialog to add Kerberos accounts"

This reverts commit 3f0c9943a5b4d5e2fdfdf321e39b027f04c105c1.

Reason for revert: Broke CrSettingsPeoplePageKerberosAccountsTest.All on linux-chromeos-dbg. See https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg/12486 for first failing build.

Original change's description:
> Add dialog to add Kerberos accounts
> 
> Adds a Chrome OS-only dialog to add Kerberos accounts and displays it
> in the Kerberos Accounts settings page when the 'Add account' button
> is clicked there. The dialog is functional, but needs further polish
> and UX review.
> 
> The functionality is guarded by the KerberosEnabled policy (off by
> default, cannot be enabled so far except for dev purposes).
> 
> BUG=chromium:952238
> TEST=Turn on KerberosEnabled policy, e.g. in YAPS or with a json file on
>      the DUT in /etc/opt/chrome/policies/managed/ with contents
>        { "KerberosEnabled": true }
>      (requires writeable rootfs). Note that there's no admin console UI
>      yet. On Chromebook, navigate to chrome:settings/kerberosAccounts,
>      click Add account. Verify that the 'Add Kerberos Account' dialog
>      opens. You might be able to log in with an Active Directory account
>      (e.g. chromeadm-lab.com), but at the time of writing the Kerberos
>      system daemon is not ready, so you should see some error.
> 
> Change-Id: I94c07c8cbbb59c9b4153929c88a534a9a36210f6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1596427
> Commit-Queue: Lutz Justen <ljusten@chromium.org>
> Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
> Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#661355}

TBR=stevenjb@chromium.org,dpapad@chromium.org,ljusten@chromium.org

Change-Id: Ic5615c3ab21cef87bb707d60fabeb7e6fc033815
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:952238
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621467
Reviewed-by: Fergus Dall <sidereal@google.com>
Commit-Queue: Fergus Dall <sidereal@google.com>
Cr-Commit-Position: refs/heads/master@{#661542}
16 files changed