Merge pull request #44956 from sato11/document-uses_transaction

Document `uses_transaction` [ci-skip]

activerecord/lib/active_record/test_fixtures.rb

@@ -67,6 +67,9 @@ module ActiveRecord
         end
       end
 
+      # Prevents automatically wrapping each specified test in a transaction,
+      # to allow application logic transactions to be tested in a top-level
+      # (non-nested) context.
       def uses_transaction(*methods)
         @uses_transaction = [] unless defined?(@uses_transaction)
         @uses_transaction.concat methods.map(&:to_s)