Remove ci_pipeline_persisted_stages feature flag

app/models/ci/pipeline.rb

@@ -401,11 +401,6 @@ module Ci
         # The `Ci::Stage` contains all up-to date data
         # as atomic processing updates all data in-bulk
         stages
-      elsif Feature.enabled?(:ci_pipeline_persisted_stages, default_enabled: true) && complete?
-        # The `Ci::Stage` contains up-to date data only for `completed` pipelines
-        # this is due to asynchronous processing of pipeline, and stages possibly
-        # not updated inline with processing of pipeline
-        stages
       else
         # In other cases, we need to calculate stages dynamically
         legacy_stages

spec/controllers/projects/pipelines_controller_spec.rb

@@ -26,10 +26,6 @@ describe Projects::PipelinesController do
     context 'when using persisted stages', :request_store do
       render_views
 
-      before do
-        stub_feature_flags(ci_pipeline_persisted_stages: true)
-      end
-
       it 'returns serialized pipelines' do
         expect(::Gitlab::GitalyClient).to receive(:allow_ref_name_caching).and_call_original
 
@@ -67,10 +63,6 @@ describe Projects::PipelinesController do
     end
 
     context 'when using legacy stages', :request_store do
-      before do
-        stub_feature_flags(ci_pipeline_persisted_stages: false)
-      end
-
       it 'returns JSON with serialized pipelines' do
         get_pipelines_index_json
 

spec/models/ci/pipeline_spec.rb

@@ -1010,7 +1010,6 @@ describe Ci::Pipeline, :mailer do
       context 'when using legacy stages' do
         before do
           stub_feature_flags(
-            ci_pipeline_persisted_stages: false,
             ci_atomic_processing: false
           )
         end
@@ -1051,7 +1050,6 @@ describe Ci::Pipeline, :mailer do
       context 'when using persisted stages' do
         before do
           stub_feature_flags(
-            ci_pipeline_persisted_stages: true,
             ci_atomic_processing: false
           )
         end

spec/serializers/pipeline_serializer_spec.rb

@@ -10,10 +10,6 @@ describe PipelineSerializer do
     described_class.new(current_user: user, project: project)
   end
 
-  before do
-    stub_feature_flags(ci_pipeline_persisted_stages: true)
-  end
-
   subject { serializer.represent(resource) }
 
   describe '#represent' do