Merge pull request #44956 from sato11/document-uses_transaction

Document `uses_transaction` [ci-skip]

(cherry picked from commit 74cd04d)

activerecord/lib/active_record/test_fixtures.rb

@@ -86,6 +86,9 @@ def setup_fixture_accessors(fixture_set_names = nil)
         include methods
       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)