Removes clusters_cte feature flag

This has been enabled on production without issue

https://gitlab.com/gitlab-org/gitlab-ce/issues/64259

app/models/concerns/deployment_platform.rb

@@ -12,19 +12,10 @@ module DeploymentPlatform
   private
   def find_deployment_platform(environment)
-    find_platform_kubernetes(environment) ||
+    find_platform_kubernetes_with_cte(environment) ||
       find_instance_cluster_platform_kubernetes(environment: environment)
   end
-  def find_platform_kubernetes(environment)
-    if Feature.enabled?(:clusters_cte)
-      find_platform_kubernetes_with_cte(environment)
-    else
-      find_cluster_platform_kubernetes(environment: environment) ||
-        find_group_cluster_platform_kubernetes(environment: environment)
-    end
-  end
-
   # EE would override this and utilize environment argument
   def find_platform_kubernetes_with_cte(_environment)
     Clusters::ClustersHierarchy.new(self).base_and_ancestors
@@ -32,18 +23,6 @@ module DeploymentPlatform
       .first&.platform_kubernetes
   end
-  # EE would override this and utilize environment argument
-  def find_cluster_platform_kubernetes(environment: nil)
-    clusters.enabled.default_environment
-      .last&.platform_kubernetes
-  end
-
-  # EE would override this and utilize environment argument
-  def find_group_cluster_platform_kubernetes(environment: nil)
-    Clusters::Cluster.enabled.default_environment.ancestor_clusters_for_clusterable(self)
-      .first&.platform_kubernetes
-  end
-
   # EE would override this and utilize environment argument
   def find_instance_cluster_platform_kubernetes(environment: nil)
     Clusters::Instance.new.clusters.enabled.default_environment

spec/models/concerns/deployment_platform_spec.rb

@@ -5,7 +5,7 @@ require 'rails_helper'
 describe DeploymentPlatform do
   let(:project) { create(:project) }
-  shared_examples '#deployment_platform' do
+  describe '#deployment_platform' do
     subject { project.deployment_platform }
     context 'with no Kubernetes configuration on CI/CD, no Kubernetes Service' do
@@ -84,20 +84,4 @@ describe DeploymentPlatform do
       end
     end
   end
-
-  context 'legacy implementation' do
-    before do
-      stub_feature_flags(clusters_cte: false)
-    end
-
-    include_examples '#deployment_platform'
-  end
-
-  context 'CTE implementation' do
-    before do
-      stub_feature_flags(clusters_cte: true)
-    end
-
-    include_examples '#deployment_platform'
-  end
 end