Merge branch 'add-db-testing-pipeline-size-change-info' into 'master'

Update database_migration_pipeline.md

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127139



Merged-by: Amy Qualls <aqualls@gitlab.com>
Approved-by: Amy Qualls <aqualls@gitlab.com>
Co-authored-by: Jon Jenkins <jjenkins@gitlab.com>