Merge branch 'vij-adjust-bbm-deletion-docs' into 'master'

Add re-queuing note to batched migration deletion

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/171394



Merged-by: Leonardo da Rosa <ldarosa@gitlab.com>
Approved-by: Leonardo da Rosa <ldarosa@gitlab.com>
Reviewed-by: Leonardo da Rosa <ldarosa@gitlab.com>
Co-authored-by: Vijay Hawoldar <vhawoldar@gitlab.com>