fix: packages/demo-nextjs/package.json to reduce vulnerabilities (#687)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NEXT-9508709

Co-authored-by: snyk-bot <snyk-bot@snyk.io>
Co-authored-by: Miguel Cardoso <miguel.cardoso@typeform.com>

Author: 3 people