Update EXAMPLES.md to fix variable usage

[deep-lyra]

Changes

The example provided had incorrect variable used for signatureVerifier. This might cause issue for someone that is copying the example and trying to run it.

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

• [ ] This change adds test coverage
• [ ] This change has been tested on the latest version of the platform/language or why not

Checklist

• [x] I have read the Auth0 general contribution guidelines
• [x] I have read the Auth0 Code of Conduct
• [x] All existing and new tests complete without errors

[jimmyjames]

❤️ Nice @deep-lyra, thanks!

@tanya732 this seems like a good contribution, can you update the branch and see what's going on with CI so we can get this in?