Merge branch 'rp/remove-old-pipeline-name-index' into 'master'

Remove unused index on ci_pipeline_metadata

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/140608



Merged-by: Prabakaran Murugesan <pmurugesan@gitlab.com>
Approved-by: Prabakaran Murugesan <pmurugesan@gitlab.com>
Co-authored-by: Reuben Pereira <rpereira@gitlab.com>