Fix Duo info card title for trial

What does this MR do and why?

The title of the GitLab Duo info card on the seat utilization page is wrong when the group has a Duo Enterprise trial, currently it says "Subscription", but it should be "Trial". This MR fixes that.

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Before	After

How to set up and validate locally

1. Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK

2. Sign in. Create new group

3. In rails console create / update new GitLab subscription for your new group

   bin/rails c
   namespace = Group.last
   gitlab_subscription = namespace.gitlab_subscription # find or create a new one if needed
   gitlab_subscription.update(hosted_plan: Plan.find_by(name: 'ultimate'))

4. Apply Duo Enterprise trial to the group

   bin/rails c
   add_on_purchase = GitlabSubscriptions::AddOnPurchase.create(subscription_add_on_id: GitlabSubscriptions::AddOn.find_by(name: 'duo_enterprise').id, namespace: Group.last, started_at: 55.days.ago, expires_on: (Date.today + 5.days), trial: true, quantity: 1, purchase_xid: '1', organization_id: 1)

5. Now go to /groups/your-group-name/-/settings/gitlab_duo/seat_utilization to verify the fix

Related to #498289