Fix trial callout to use the correct plan

namespaces.plan_id is unused and we should use the plan in
the gitlab_subscriptions table

ee/app/views/shared/billings/_trial_status.html.haml

@@ -5,7 +5,7 @@
 - if namespace.eligible_for_trial?
   = s_("BillingPlans|Learn more about each plan by reading our %{faq_link}, or start a free 30-day trial of GitLab.com Gold.").html_safe % { faq_link: faq_link }
 - elsif namespace.trial_active?
-  = s_("BillingPlans|Your GitLab.com %{plan} trial will <strong>expire after %{expiration_date}</strong>. You can retain access to the %{plan} features by upgrading below.").html_safe % { plan: namespace.plan&.title, expiration_date: namespace.trial_ends_on }
+  = s_("BillingPlans|Your GitLab.com %{plan} trial will <strong>expire after %{expiration_date}</strong>. You can retain access to the %{plan} features by upgrading below.").html_safe % { plan: namespace.gitlab_subscription&.plan_title, expiration_date: namespace.trial_ends_on }
 - elsif namespace.trial_expired?
   = s_("BillingPlans|Your GitLab.com trial expired on %{expiration_date}. You can restore access to the features at any time by upgrading below.").html_safe % { expiration_date: namespace.trial_ends_on }
 - else

ee/spec/helpers/ee/user_callouts_helper_spec.rb

@@ -201,7 +201,10 @@ describe EE::UserCalloutsHelper do
         allow(helper).to receive(:show_gold_trial?) { show_gold_trial? }
         allow(helper).to receive(:user_default_dashboard?) { user_default_dashboard? }
         allow(helper).to receive(:has_some_namespaces_with_no_trials?) { has_some_namespaces_with_no_trials? }
-        namespace.update(plan: gold_plan) unless has_no_trial_or_gold_plan?
+
+        unless has_no_trial_or_gold_plan?
+          create(:gitlab_subscription, hosted_plan: gold_plan, namespace: namespace)
+        end
       end
 
       it do

ee/spec/views/shared/billings/_trial_status.html.haml_spec.rb

@@ -6,18 +6,12 @@ describe 'shared/billings/_trial_status.html.haml' do
   include ApplicationHelper
 
   let_it_be(:group) { create(:group) }
-  let_it_be(:gitlab_subscription) { create(:gitlab_subscription, namespace: group) }
   let(:plan) { nil }
   let(:trial_ends_on) { nil }
   let(:trial) { false }
 
   before do
-    gitlab_subscription.update(
-      hosted_plan: plan,
-      trial_ends_on: trial_ends_on,
-      trial: trial
-    )
-    group.update(plan: plan)
+    create(:gitlab_subscription, namespace: group, hosted_plan: plan, trial_ends_on: trial_ends_on, trial: trial)
   end
 
   context 'when not eligible for trial' do