Remove trial button from free billing page if trialed before

What does this MR do and why?

Remove trial button from free billing page if trialed before

• namespace can not start a trial if they already have had one on this namespace.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Turn on billing features in the app(via rails console)

   ApplicationSetting.first.update(check_namespace_plan: true)

2. Configure to act as SaaS and restart gdk.
3. Create a new group.
4. Change line in ee/app/views/groups/billings/_free_plan_billing_index.html.haml from - if namespace.never_had_trial? to - if !namespace.never_had_trial?
5. Visit that group's overview page such as http://localhost:3000/flightjs
6. Find the billing link under settings.
7. Click the billing link.
8. Observe the billing page.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #420592 (closed)