fix: example/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-6928867

Author: snyk-bot

example/requirements.txt

@@ -4,3 +4,4 @@ gunicorn
 oic>=1.2.1
 setuptools>=65.5.1 # not directly required, pinned by Snyk to avoid a vulnerability
 werkzeug>=3.0.1 # not directly required, pinned by Snyk to avoid a vulnerability
+requests>=2.32.0 # not directly required, pinned by Snyk to avoid a vulnerability