Fix autofill related crash due to our disabling of optimization hints

[emerick]

Resolves brave/brave-browser#33426

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
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• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run lint, npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
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After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[mkarolin]

I was thinking in case we ever decide to flip the feature back on and not necessarily remember about this override it might be good to make this depend on the feature, same as in https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/optimization_guide/optimization_guide_keyed_service_factory.cc;l=19, like

#include "components/optimization_guide/core/optimization_guide_features.h"

AutofillOptimizationGuide* GetAutofillOptimizationGuide() const override {
  if (optimization_guide::features::IsOptimizationHintsEnabled()) {
    return ChromeAutofillClient::GetAutofillOptimizationGuide();
  }
  return nullptr;
}

[emerick]

Yeah, that makes sense, fixed.

[bsclifton]

Great call, @mkarolin 😄

[mkarolin]

LGTM 👍

[bsclifton]

++! 😄

[MadhaviSeelam]

Verification PASSED using

Brave | 1.61.3 Chromium: 118.0.5993.54 (Official Build) nightly (64-bit)
-- | --
Revision | 65de72604895b354f3a9c4ad818b993028096814
OS | Windows 11 Version 22H2 (Build 22621.2283)

Verified using the original STR from brave/brave-browser#33426 (comment)

Confirmed no crash occurred and Send a Wire or ACH transfer page is shown as expected