[appsync] I want to fix example code

[ufoo68]

doc page: https://docs.aws.amazon.com/cdk/api/latest/docs/aws-appsync-readme.html

I want to fix example code

const userPool = new UserPool(this, 'UserPool'{
      userPoolName: 'myPool',
    });

to

const userPool = new UserPool(this, 'UserPool', {
      userPoolName: 'myPool',
    });

---

This is a 📕 documentation issue

[shivlaks]

closed by #8765