add missing callback example

[elen-ita]

Description

I was implementing the lib in our of our projects and realized this example was missing setting callback to false.

Testing

• [ ] This change adds test coverage for new/changed/fixed functionality

Checklist

• [ ] I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• [ ] All active GitHub checks for tests, formatting, and security are passing
• [ ] The correct base branch is being used, if not the default branch