Merge branch 'eb-add-unlock-pipelines-extra-low-concurrency' into 'master'

Add extra low concurrency flag for unlock pipelines worker

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/140318



Merged-by: Stan Hu <stanhu@gmail.com>
Approved-by: Heinrich Lee Yu <heinrich@gitlab.com>
Approved-by: Max Orefice <morefice@gitlab.com>
Approved-by: Stan Hu <stanhu@gmail.com>
Reviewed-by: Max Orefice <morefice@gitlab.com>
Co-authored-by: Erick Bajao <fbajao@gitlab.com>