CrOS Settings: Update account manager URL from Ash browser

When the OsSettingsRevampWayfinding feature flag is enabled, the
account manager subpage is up-leveled to the top-level Accounts page.
This CL updates the route accordingly under such conditions.
Screen recording: http://shortn/_CApLv99tq1

Bug: b:326311639
Test: Manually verify UI
Change-Id: Ia337662515fe97bc9c9b8753fd15e8cf10db384e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5336578


Reviewed-by: Anastasiia N <anastasiian@chromium.org>
Commit-Queue: Wes Okuhara <wesokuhara@google.com>
Cr-Commit-Position: refs/heads/main@{#1267442}