Enable FF ci_auto_cancel_all_pipelines by default

changelogs/unreleased/275997-enable-ci_auto_cancel_all_pipelines.yml

+---
+title: Allow canceling all pipelines with auto-cancel
+merge_request: 47906
+author:
+type: fixed

config/feature_flags/development/ci_auto_cancel_all_pipelines.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/275997
 milestone: '13.6'
 type: development
 group: group::pipeline authoring
-default_enabled: false
+default_enabled: true

lib/gitlab/ci/pipeline/chain/cancel_pending_pipelines.rb

@@ -35,7 +35,7 @@ module Gitlab
           # rubocop: enable CodeReuse/ActiveRecord
 
           def pipelines
-            if ::Feature.enabled?(:ci_auto_cancel_all_pipelines, project, default_enabled: false)
+            if ::Feature.enabled?(:ci_auto_cancel_all_pipelines, project, default_enabled: true)
               project.all_pipelines.ci_and_parent_sources
             else
               project.ci_pipelines