OpenZeppelin/canton-contracts: test/placeholder/daml/OpenZeppelin/PlaceholderTest.daml

Daml contract source - OpenZeppelin/canton-contracts/test/placeholder/daml/OpenZeppelin/PlaceholderTest.daml ```daml -- | Placeholder keeping test/ present in git until the first component -- graduates from experiments/. Delete alongside this package when real -- tests arrive. module OpenZeppelin.Pl