Resolve cross join issues in ee/lib/ee/gitlab/background_migration/backfill_finding_initial_pipeline_id.rb
What does this MR do and why?
The named migration was finalized in %17.3 which was a required stop for GitLab. As such, it should be safe to remove this MR to avoid needing to resolve the cross join issue that won't function post sec-decomposition.
MR acceptance checklist
Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.
Related to #480364 (closed)