An entrypoint for a pending administrator. A pending administrator must just call it and he will become a new administrator of the contract.
An entrypoint doesn't accept any parameters.
const proxyMinterAddress = "KT1...";
const proxyMinter = await tezos.contract.at(proxyMinterAddress);
const operation = await proxyMinter.methods.confirm_admin().send();
senderof the transaction is not current pending administrator (not the address that was assigned by the current administrator to the shift).