[Autofill Assistant] Remove the preference entry.

Before this patch, we would show a preference entry to enable/disable
Autofill Assistant. The way onboarding works, this is no longer desired.

This patch always removes the preference from the xml so that the patch
is smaller and less controversial to be merged into the release branch.

After this patch, enableing/disabling the feature will entirely be done
during the onboarding flow.

Bug: 806868
Change-Id: I1b10f9cfb55e2d4cf320259f12ed7c3c9fb395c6
Reviewed-on: https://chromium-review.googlesource.com/c/1368649
Commit-Queue: Mathias Carlen <mcarlen@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616266}
2 files changed