Remove duplicated method and follow CE changes

app/models/concerns/deployment_platform.rb

 module DeploymentPlatform
-  def deployment_platform(environment: nil)
+  def deployment_platform
     @deployment_platform ||=
       find_cluster_platform_kubernetes ||
       find_kubernetes_service_integration ||

app/models/environment.rb

@@ -137,10 +137,6 @@ class Environment < ActiveRecord::Base
     end
   end
 
-  def deployment_platform
-    project.deployment_platform(environment: self)
-  end
-
   def has_terminals?
     deployment_platform.present? && available? && last_deployment.present?
   end