Merge branch '469056-drop-ci_pipelines_config-follow-up' into 'master'

Simplify DropCiPipelinesConfig migration

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/170540



Merged-by: Leonardo da Rosa <ldarosa@gitlab.com>
Approved-by: Tianwen Chen <tchen@gitlab.com>
Approved-by: Leonardo da Rosa <ldarosa@gitlab.com>
Co-authored-by: Marius Bobin <mbobin@gitlab.com>