Revert "Reland "Retrigger form parsing on Autofill ML model load""

This reverts commit b7c62a3625976264873892637ef1ca01e2f0868c.

Reason for revert: Suspected to be the cause of https://crbug.com/440029649

Bug: 435412093, 440029649
Original change's description:
> Reland "Retrigger form parsing on Autofill ML model load"
>
> This is a reland of commit a1d0f11db3dfcaf87e88be99627b113dcd8f09b3
>
> It is much simpler, moving all the reparsing logic into AutofillManager.
>
> Original change's description:
> > Retrigger form parsing on Autofill ML model load
> >
> > AutofillClient creates a model handler and subscribes to its
> > OnModelChanged updates via a CallbackList and CallbackListSubscription.
> > There is one subscription object for each of Autofill and PWM. The
> > subscription happens in the
> > `Get<Autofill|PasswordManager>FieldClassificationModelHandler`
> > functions.
> >
> > It was considered as an alternative to instead put the subscription
> > operation in the AutofillClient constructor - however, this would mean
> > that the model is essentially loaded on startup, since an AutofillClient
> > is immediately created for the startup page.
> >
> > When the model loads, the new method `AutofillClient::OnModelChanged` is
> > called.
> >
> > This calls the new method `AutofillDriverFactory::ReparseKnownForms`.
> >
> > This calls `OnFormsSeen` on each driver's own forms.
> >
> > Bug: 435412093
> >
> > Change-Id: I768bd698948bcf57d8662ff82a4adf3c42ae956b
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6807309
> > Reviewed-by: Bruno Braga <brunobraga@google.com>
> > Reviewed-by: Rohit Rao <rohitrao@chromium.org>
> > Commit-Queue: Teo Lamort de Gail <lamort@google.com>
> > Reviewed-by: Dominic Battré <battre@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1500788}
>
> Bug: 435412093
> Change-Id: Idd7766e94e577dcd8c8c5f68ae7829a9dc055155
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6850141
> Reviewed-by: Karol Sygiet <sygiet@google.com>
> Reviewed-by: Christoph Schwering <schwering@google.com>
> Commit-Queue: Teo Lamort de Gail <lamort@google.com>
> Cr-Commit-Position: refs/heads/main@{#1503807}

Bug: 435412093, 440029649
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I4d8dd8ae4c55904cea1d2341f9806f9c7cb3c5c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6864181
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Mahmoud Rashad <mmrashad@google.com>
Commit-Queue: Mahmoud Rashad <mmrashad@google.com>
Cr-Commit-Position: refs/heads/main@{#1503870}