Update passing `string` as error with `object`

[oa-s]

instead of using error we need to pass object {message: "error mesage", code: 1} @hboon could u please make pr to this repo with changes, needs for https://github.com/AlphaWallet/alpha-wallet-ios/issues/6456 we actually need to use const response = {'id': id, jsonrpc: '2.0', result: value, error: error } instead of const response = {'id': id, jsonrpc: '2.0', result: value, error: {message: error} }