Fix ingestion logic for remediations
What does this MR do and why?
This MR fixes the source of finding ids so that we update vulnerability read entries properly for has_remediations field.
The change was first introduced in !129125 (diffs). This creates some inconsistency in data which will be fixed in a subsequent MR by re-queuing modified backfill batched migration lib/gitlab/background_migration/backfill_has_remediations_of_vulnerability_reads.rb.
How to set up and validate locally
Related to #429361 (closed)
Edited by Subashis Chakraborty