Remove remaining FF alert_management_minimal

Follow-up to
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/31171

app/services/projects/prometheus/alerts/notify_service.rb

@@ -117,8 +117,6 @@ module Projects
         end
 
         def process_prometheus_alerts
-          return unless Feature.enabled?(:alert_management_minimal, project)
-
           alerts.each do |alert|
             AlertManagement::ProcessPrometheusAlertService
               .new(project, nil, alert.to_h)

spec/services/projects/prometheus/alerts/notify_service_spec.rb

@@ -225,11 +225,6 @@ describe Projects::Prometheus::Alerts::NotifyService do
         create(:project_alerting_setting, project: project, token: token)
       end
 
-      context 'when alert_management_minimal feature enabled' do
-        before do
-          stub_feature_flags(alert_management_minimal: true)
-        end
-
       context 'with multiple firing alerts and resolving alerts' do
         let(:payload_raw) do
           payload_for(firing: [alert_firing, alert_firing], resolved: [alert_resolved])
@@ -248,20 +243,6 @@ describe Projects::Prometheus::Alerts::NotifyService do
       end
     end
 
-      context 'when alert_management_minimal feature disabled' do
-        before do
-          stub_feature_flags(alert_management_minimal: false)
-        end
-
-        it 'does not process Prometheus alerts' do
-          expect(AlertManagement::ProcessPrometheusAlertService)
-            .not_to receive(:new)
-
-          subject
-        end
-      end
-    end
-
     context 'process incident issues' do
       before do
         create(:prometheus_service, project: project)