fix: requirements-dev.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390193
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390194

Author: snyk-bot

requirements-dev.txt

@@ -5,3 +5,4 @@ pytest>=6.2.1
 twine==3.3.0
 pypandoc>=1.5
 wheel>=0.31.0
+urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability