fix: pip-sample/testing_requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-WERKZEUG-6808933

pip-sample/testing_requirements.txt

@@ -62,7 +62,7 @@ urllib3==1.26.5
 virtualenv==16.0.0
 wcwidth==0.1.7
 webencodings==0.5.1
-Werkzeug==0.15.3
+Werkzeug==3.0.3
 widgetsnbextension==3.4.2
 xlrd==1.1.0
 django==3.2.16