Move combined trial params to correct trial creation flow

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/468028

What does this MR do and why?

Moves the CDot trial creation params to the correct trial registration flow.

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.

Screenshots or screen recordings

There are no visual changes

How to set up and validate locally

1. Setup CDot locally - https://gitlab.com/gitlab-org/customers-gitlab-com/-/tree/b263f1abe9db0c1c8098471b9b6d8476dc8c1f77#setup
2. Set GL env var to local CDot via: CUSTOMER_PORTAL_URL=http://localhost:5000/
3. Create a new GL user
4. Signup for Ultimate trial
5. Verify you also got the Duo Enterprise account.

Related to #468028