Remove :kubernetes_namespace_per_environment feature flag

Feature flag has been defaulting to `true` since 12.2

app/services/clusters/create_service.rb

@@ -37,7 +37,7 @@ module Clusters
     end
 
     def global_params
-      { user: current_user, namespace_per_environment: Feature.enabled?(:kubernetes_namespace_per_environment, default_enabled: true) }
+      { user: current_user }
     end
 
     def clusterable_params

spec/support/services/clusters/create_service_shared.rb

@@ -32,11 +32,6 @@ shared_context 'invalid cluster create params' do
 end
 
 shared_examples 'create cluster service success' do
-  context 'namespace per environment feature is enabled' do
-    before do
-      stub_feature_flags(kubernetes_namespace_per_environment: true)
-    end
-
   it 'creates a cluster object and performs a worker' do
     expect(ClusterProvisionWorker).to receive(:perform_async)
 
@@ -56,33 +51,6 @@ shared_examples 'create cluster service success' do
     expect(subject.platform).to be_nil
     expect(subject.namespace_per_environment).to eq true
   end
-  end
-
-  context 'namespace per environment feature is disabled' do
-    before do
-      stub_feature_flags(kubernetes_namespace_per_environment: false)
-    end
-
-    it 'creates a cluster object and performs a worker' do
-      expect(ClusterProvisionWorker).to receive(:perform_async)
-
-      expect { subject }
-        .to change { Clusters::Cluster.count }.by(1)
-        .and change { Clusters::Providers::Gcp.count }.by(1)
-
-      expect(subject.name).to eq('test-cluster')
-      expect(subject.user).to eq(user)
-      expect(subject.project).to eq(project)
-      expect(subject.provider.gcp_project_id).to eq('gcp-project')
-      expect(subject.provider.zone).to eq('us-central1-a')
-      expect(subject.provider.num_nodes).to eq(1)
-      expect(subject.provider.machine_type).to eq('machine_type-a')
-      expect(subject.provider.access_token).to eq(access_token)
-      expect(subject.provider).to be_legacy_abac
-      expect(subject.platform).to be_nil
-      expect(subject.namespace_per_environment).to eq false
-    end
-  end
 end
 
 shared_examples 'create cluster service error' do