Remove ci_lower_frequency_trace_update feature flag

Turn the 60s trace interval update the default behavior.

changelogs/unreleased/fp-remove-ff-ci-lower-frequency-trace-update.yml

+---
+title: Remove ci_lower_frequency_trace_update feature flag
+merge_request: 57713
+author:
+type: performance

config/feature_flags/development/ci_lower_frequency_trace_update.yml

----
-name: ci_lower_frequency_trace_update
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/56743
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/324768 
-milestone: '13.11'
-type: development
-group: group::continuous integration
-default_enabled: false

lib/gitlab/ci/trace.rb

@@ -11,7 +11,6 @@ module Gitlab
       LOCK_SLEEP = 0.001.seconds
       WATCH_FLAG_TTL = 10.seconds
 
-      LEGACY_UPDATE_FREQUENCY_DEFAULT = 30.seconds
       UPDATE_FREQUENCY_DEFAULT = 60.seconds
       UPDATE_FREQUENCY_WHEN_BEING_WATCHED = 3.seconds
 
@@ -118,11 +117,7 @@ module Gitlab
         if being_watched?
           UPDATE_FREQUENCY_WHEN_BEING_WATCHED
         else
-          if Feature.enabled?(:ci_lower_frequency_trace_update, job.project, default_enabled: :yaml)
-            UPDATE_FREQUENCY_DEFAULT
-          else
-            LEGACY_UPDATE_FREQUENCY_DEFAULT
-          end
+          UPDATE_FREQUENCY_DEFAULT
         end
       end
 

spec/lib/gitlab/ci/trace_spec.rb

@@ -64,14 +64,6 @@ RSpec.describe Gitlab::Ci::Trace, :clean_gitlab_redis_shared_state, factory_defa
   describe '#update_interval' do
     context 'it is not being watched' do
       it { expect(trace.update_interval).to eq(60.seconds) }
-
-      context 'when feature flag ci_lower_frequency_trace_update is disabled' do
-        before do
-          stub_feature_flags(ci_lower_frequency_trace_update: false)
-        end
-
-        it { expect(trace.update_interval).to eq(30.seconds) }
-      end
     end
 
     context 'it is being watched' do

spec/requests/api/ci/runner/jobs_trace_spec.rb

@@ -216,19 +216,6 @@ RSpec.describe API::Ci::Runner, :clean_gitlab_redis_shared_state do
             expect(response).to have_gitlab_http_status(:accepted)
             expect(response.header['X-GitLab-Trace-Update-Interval']).to eq('60')
           end
-
-          context 'when ci_lower_frequency_trace_update feature flag is disabled' do
-            before do
-              stub_feature_flags(ci_lower_frequency_trace_update: false)
-            end
-
-            it 'returns the legacy interval in X-GitLab-Trace-Update-Interval' do
-              patch_the_trace
-
-              expect(response).to have_gitlab_http_status(:accepted)
-              expect(response.header['X-GitLab-Trace-Update-Interval']).to eq('30')
-            end
-          end
         end
       end