Remove dag_pipeline_tab flag

Removes from frontend and backend

app/assets/javascripts/pipelines/pipeline_details_dag.js

@@ -12,7 +12,7 @@ const apolloProvider = new VueApollo({
 const createDagApp = () => {
   const el = document.querySelector('#js-pipeline-dag-vue');
 
-  if (!window.gon?.features?.dagPipelineTab || !el) {
+  if (!el) {
     return;
   }
 

app/controllers/projects/pipelines_controller.rb

@@ -12,7 +12,6 @@ class Projects::PipelinesController < Projects::ApplicationController
   before_action :authorize_create_pipeline!, only: [:new, :create, :config_variables]
   before_action :authorize_update_pipeline!, only: [:retry, :cancel]
   before_action do
-    push_frontend_feature_flag(:dag_pipeline_tab, project, default_enabled: true)
     push_frontend_feature_flag(:pipelines_security_report_summary, project)
     push_frontend_feature_flag(:new_pipeline_form, project, default_enabled: true)
     push_frontend_feature_flag(:graphql_pipeline_header, project, type: :development, default_enabled: false)

app/views/projects/pipelines/_with_tabs.html.haml

 - return if pipeline_has_errors
-- dag_pipeline_tab_enabled = Feature.enabled?(:dag_pipeline_tab, @project, default_enabled: true)
 
 .tabs-holder
   %ul.pipelines-tabs.nav-links.no-top.no-bottom.mobile-separator.nav.nav-tabs
     %li.js-pipeline-tab-link
       = link_to project_pipeline_path(@project, @pipeline), data: { target: '#js-tab-pipeline', action: 'pipelines', toggle: 'tab' }, class: 'pipeline-tab' do
         = _('Pipeline')
-    - if dag_pipeline_tab_enabled
     %li.js-dag-tab-link
       = link_to dag_project_pipeline_path(@project, @pipeline), data: { target: '#js-tab-dag', action: 'dag', toggle: 'tab' }, class: 'dag-tab' do
         = _('Needs')
@@ -79,7 +77,6 @@
                     %code.bash.js-build-output
                       = build_summary(build)
 
-  - if dag_pipeline_tab_enabled
   #js-tab-dag.tab-pane
     #js-pipeline-dag-vue{ data: { pipeline_project_path: @project.full_path, pipeline_iid: @pipeline.iid, empty_svg_path: image_path('illustrations/empty-state/empty-dag-md.svg'), about_dag_doc_path: help_page_path('ci/directed_acyclic_graph/index.md'), dag_doc_path: help_page_path('ci/yaml/README.md', anchor: 'needs')} }
 

config/feature_flags/development/dag_pipeline_tab.yml

----
-name: dag_pipeline_tab
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/30310
-rollout_issue_url: 
-milestone: '13.0'
-type: development
-group: group::pipeline authoring
-default_enabled: true

doc/ci/directed_acyclic_graph/index.md

@@ -82,11 +82,8 @@ are certain use cases that you may need to work around. For more information:
 ## Needs Visualization
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/215517) in GitLab 13.1 as a [Beta feature](https://about.gitlab.com/handbook/product/#beta).
-> - It was deployed behind a feature flag, disabled by default.
-> - It became [enabled by default](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/36802) in 13.2.
 > - It became a [standard feature](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38517) in 13.3.
-> - It's enabled on GitLab.com.
-> - For GitLab self-managed instances, GitLab administrators can opt to [disable it](#enable-or-disable-needs-visualization).
+> - [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52208) in GitLab 13.9.
 
 The needs visualization makes it easier to visualize the relationships between dependent jobs in a DAG. This graph displays all the jobs in a pipeline that need or are needed by other jobs. Jobs with no relationships are not displayed in this view.
 
@@ -97,16 +94,3 @@ To see the needs visualization, click on the **Needs** tab when viewing a pipeli
 Clicking a node highlights all the job paths it depends on.
 
 ![Needs visualization with path highlight](img/dag_graph_example_clicked_v13_1.png)
-
-### Enable or disable Needs Visualization **(CORE ONLY)**
-
-The needs visualization is deployed behind a feature flag that is **enabled by default**.
-[GitLab administrators with access to the GitLab Rails console](../../administration/feature_flags.md)
-can opt to disable it for your instance:
-
-```ruby
-# Instance-wide
-Feature.disable(:dag_pipeline_tab)
-# or by project
-Feature.disable(:dag_pipeline_tab, Project.find(<project ID>))
-```

spec/features/projects/pipelines/pipeline_spec.rb

@@ -626,20 +626,6 @@ RSpec.describe 'Pipeline', :js do
         end
       end
     end
-
-    context 'when FF dag_pipeline_tab is disabled' do
-      before do
-        stub_feature_flags(dag_pipeline_tab: false)
-        visit_pipeline
-      end
-
-      it 'does not show DAG link' do
-        expect(page).to have_link('Pipeline')
-        expect(page).to have_link('Jobs')
-        expect(page).not_to have_link('DAG')
-        expect(page).to have_link('Failed Jobs')
-      end
-    end
   end
 
   context 'when user does not have access to read jobs' do