Add comments explaininng no-ops

db/post_migrate/20210811193033_add_unique_index_to_vulnerability_finding_links.rb → db/migrate/20210811193033_add_unique_index_to_vulnerability_finding_links.rb

 # frozen_string_literal: true
 
 class AddUniqueIndexToVulnerabilityFindingLinks < Gitlab::Database::Migration[1.0]
+  # This migration has been moved to db/post_migrate/20220201193033_add_unique_index_to_vulnerability_finding_links_with_truncate.rb
+  # Previously, this was causing an bug where there was a conflict between the table cleanup and the index creation.
+
   def up
     # no op
   end

db/post_migrate/20211104165220_remove_vulnerability_finding_links.rb

 # frozen_string_literal: true
 
 class RemoveVulnerabilityFindingLinks < Gitlab::Database::Migration[1.0]
+  # This migration has been moved to a TRUNCATE in db/post_migrate/20220201193033_add_unique_index_to_vulnerability_finding_links_with_truncate.rb
+  # Previously, this was causing an bug where there was a conflict between the table cleanup and the index creation.
+
   def up
     # no op
   end

db/post_migrate/20211210173137_remove_vulnerability_finding_links_again.rb

 # frozen_string_literal: true
 
 class RemoveVulnerabilityFindingLinksAgain < Gitlab::Database::Migration[1.0]
+  # This migration has been moved to a TRUNCATE in db/post_migrate/20220201193033_add_unique_index_to_vulnerability_finding_links_with_truncate.rb
+  # Previously, this was causing an bug where there was a conflict between the table cleanup and the index creation.
+
   def up
     # no op
   end