Default pipeline graph feature flag to true

* Defaults the `:graphql_pipeline_details` feature flag to true.
* Updates documentation

changelogs/unreleased/276949-docs-and-default.yml

+---
+title: 'Update Pipeline Graph Visualization'
+merge_request: 58889
+author:
+type: changed

config/feature_flags/development/graphql_pipeline_details.yml

@@ -4,4 +4,4 @@ introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46380
 rollout_issue_url:
 type: development
 group: group::pipeline authoring
-default_enabled: false
+default_enabled: true

doc/ci/pipelines/index.md

@@ -332,10 +332,12 @@ GitLab capitalizes the stages' names in the pipeline graphs.
 
 ### Regular pipeline graphs
 
+> - [Visualization improved](https://gitlab.com/gitlab-org/gitlab/-/issues/276949) in GitLab 13.11.
+
 Regular pipeline graphs show the names of the jobs in each stage. Regular pipeline graphs can
 be found when you are on a [single pipeline page](#view-pipelines). For example:
 
-![Pipelines example](img/pipelines.png)
+![Pipelines example](img/pipelines_v13_11.png)
 
 [Multi-project pipeline graphs](../multi_project_pipelines.md#multi-project-pipeline-visualization) help
 you visualize the entire pipeline, including all cross-project inter-dependencies. **(PREMIUM)**