Move enum specific code from a concern to CI stage

app/models/ci/stage.rb

@@ -5,7 +5,7 @@ module Ci
     include HasStatus
     include Gitlab::OptimisticLocking
 
-    enumerate_status!
+    enum status: HasStatus::STATUSES_ENUM
 
     belongs_to :project
     belongs_to :pipeline

app/models/concerns/has_status.rb

@@ -12,10 +12,6 @@ module HasStatus
                     failed: 4, canceled: 5, skipped: 6, manual: 7 }.freeze
 
   class_methods do
-    def enumerate_status!
-      enum status: HasStatus::STATUSES_ENUM
-    end
-
     def status_sql
       scope_relevant = respond_to?(:exclude_ignored) ? exclude_ignored : all
       scope_warnings = respond_to?(:failed_but_allowed) ? failed_but_allowed : none