Fix Missing 'Invite more members' CTA on 'Learn GitLab' page

What does this MR do and why?

Fixes the bug described in #417185 (closed) where the Invite more members button is missing on the learn gitlab page

Screenshots or screen recordings

Before	After

How to set up and validate locally

Since it is hard to create a trial in development, due to CustomersDot dependencies, we can rely on the test added in ee/spec/features/learn_gitlab_spec.rb

or...

1. Setup to simulate SaaS and restart GDK
   • Make sure Admin > Settings > General > Sign Up Restrictions match the below (no admin approval, but hard email confirmation)
2. Register as a new user.
3. Confirm email by finding the confirmation path from last User created in rails console
   • Rails.application.routes.url_helpers.user_confirmation_path(confirmation_token: User.last.confirmation_token)
4. Visit the path from the previous step.
5. You should be on the sign in page, log back in.
6. Select any 'role' and 'Just me' in the welcome form after sign up step.
7. Choose 'Create a new project'
8. Click 'Continue'
9. Fill out fields to create a group and project on the next page.
10. Click 'Create project'
11. Verify you get to the onboarding and page refreshes to provide a "Ok, let's go" button.
12. Click on "Ok, let's go" and verify you are dropped into the learn gitlab project and the celebrate modal pops up with confetti
13. Go to ee/app/views/shared/_unlimited_members_during_trial_alert.html.haml and remove this line - return unless show_unlimited_members_during_trial_alert?(root_namespace)
14. Close the modal that was open and reload the page to see the alert.

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 #417185 (closed)