Improve PullPayment docs (#1965)
Improve PullPayment docs (#1965)

* Improve PullPayment docs

* Reword escrow note

* Update contracts/payment/PullPayment.sol

Co-Authored-By: Francisco Giordano <4223852eec80914c4c190cdc031e06592b151a67@gmail.com>

OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity,OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity