Fix a false negative for `FactoryBot/AssociationStyle` when using implicit associations in global traits

[r7kamura]

Implicit associations inside global trait definitions with EnforcedStyle: explicit were not being detected as offenses:

FactoryBot.define do
  trait :with_user do
    user
  # ^^^^
  end
end

but I believe they should be, so I’ve changed the behavior accordingly.

There’s a chance I might be misunderstanding how FactoryBot is supposed to be used, so please don’t hesitate to tell me if anything feels off 🙇

---

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