Schedule removal of duplicate Findings

What does this MR do?

This migration reschedules RemoveDuplicateVulnerabilitiesFindings background migration since we still have duplicate entires (at least on gprd-db-archive) according to the query below

Related to #292239 (closed)

Find duplicates query

SELECT DISTINCT report_type, location_fingerprint, primary_identifier_id, project_id, array_agg(id) as ids, array_agg(uuid) as uuids
FROM vulnerability_occurrences
GROUP BY report_type, location_fingerprint, primary_identifier_id, project_id
HAVING (COUNT(*) > 1);

Query timings are available over at !49937 (merged)

Updates query timings

Cold Query for batch of 5000: ~3000ms https://console.postgres.ai/gitlab/gitlab-production-tunnel/sessions/2504/commands/7672 Warm Query for batch of 5000: ~300ms https://console.postgres.ai/gitlab/gitlab-production-tunnel/sessions/2504/commands/7673

7544976 rows in vulnerability_occurrences / 5000 rows per batch = 1509 batches

2 minute interval * 1509 batches = 3018 min => 50.3 hours

Thanks @sabrams

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