Remove ab_test_args stub analytics properties

[aduth]

🛠 Summary of changes

Updates controller specs to remove ab_test_args method stubbing.

Why?

• We should want to know exactly what's logged, including both the value and the keyword argument being part of affected analytics event method signatures
  • Documenting the keyword arguments will cause them to be visible on Analytics Events internal handbook page
• These aren't really A/B tests, they're just properties controlled by a feature flag
• This will simplify the effort to remove the in-person proofing opt-in feature flag, which has already been live in production for many months now
• The properties are already documented for many analytics events where we're not stubbing the result, so this brings consistency
• Allows for removing allowed_extra_analytics exceptions, particularly in feature specs, where the logged output would match more what's in the real-world, and wouldn't benefit from the stubbing implemented in controller specs

Draft until verified if CI builds reveal any unnecessary allowed_extra_analytics to be removed.

📜 Testing Plan

Verify build passes.