Do not show cloud licensing banner when subscription is already on cloud

This addresses #385768 (closed).

What does this MR do and why?

This MR changes the logic of displaying the cloud licensing banner do show it only when the user is under a legacy license. Please refer to the parent issue for details on why we're doing this.

Screenshots or screen recordings

Before:

After:

How to set up and validate locally

1. Checkout this branch
2. Set export GITLAB_LICENSE_MODE=test, and ensure GITLAB_SIMULATE_SAAS is not set to truthy value (unset GITLAB_SIMULATE_SAAS)
3. Start GDK
4. Navigate to <GDK URL>/admin/subscription
5. Add a cloud activation code
6. Verify banner is not displayed
7. Remove the license
8. Navigate to <GDK URL>/admin/application_settings/general
9. Scroll to "Add License"
10. Add a legacy license
11. Verify the banner is displayed

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.