Use onboarding status instead of direct com

What does this MR do and why?

Match trial registrations helper for com feature to the one used for onboarding

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

bin/rails c

> Feature.enable(:free_trial_registration_redesign)

• Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK
• Sign out. Visit /-/trial_registrations/new
• Make sure page loads without any errors.

bin/rails c

> Feature.disable(:free_trial_registration_redesign)

• Visit /-/trial_registrations/new. Make sure page loads without any errors.

Related to #429116 (closed)