Remove dead company-form onboarding leftovers

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Problem

!253445 (merged) removes CompanyController and its layers. CompanyController was the only caller of Onboarding::StatusStepUpdateService, and the deleted company view was the only consumer of a set of company-form predicate methods. Once that MR merges, this code has no remaining production callers.

Proposal

• Remove Onboarding::StatusStepUpdateService (ee/app/services/onboarding/status_step_update_service.rb) and its spec
• Remove redirect_to_company_form? from Onboarding::FreeRegistration and Onboarding::TrialRegistration
• Remove show_company_form_side_column? and show_company_form_footer? from Onboarding::TrialRegistration and Onboarding::AutomaticTrialRegistration
• Remove the matching delegate lines in ee/app/presenters/ee/onboarding/status_presenter.rb
• Remove the specs covering all of the above

Notes

Onboarding::AutomaticTrialRegistration itself is still live: Onboarding::UserStatus#registration_type returns it for the free-to-trial conversion path. Only its two company-form predicate overrides are dead, not the class itself.

Blocked on !253445 (merged) merging first.