Inconsistent schema - index

Add index_vulnerability_occurrences_deduplication index back

Changelog: fixed

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/349549

db/post_migrate/20220109134455_add_idx_vulnerability_occurrences_dedup_again.rb

+# frozen_string_literal: true
+
+class AddIdxVulnerabilityOccurrencesDedupAgain < Gitlab::Database::Migration[1.0]
+  TABLE = :vulnerability_occurrences
+  INDEX_NAME = 'index_vulnerability_occurrences_deduplication'
+  COLUMNS = %i[project_id report_type project_fingerprint]
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index TABLE, COLUMNS, name: INDEX_NAME
+  end
+
+  def down
+    # nothing to do here
+  end
+end

db/schema_migrations/20220109134455

+fee092680e22e579ea51f776d11bbfd6a49b936e4ab776760a153ce613e7a0cd
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