fix: requirements_dev.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-CERTIFI-3164749
- https://snyk.io/vuln/SNYK-PYTHON-CERTIFI-5805047
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-6150717
- https://snyk.io/vuln/SNYK-PYTHON-PYGMENTS-1086606
- https://snyk.io/vuln/SNYK-PYTHON-PYGMENTS-1088505
- https://snyk.io/vuln/SNYK-PYTHON-PYGMENTS-5750273
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-5595532

requirements_dev.txt

@@ -10,3 +10,7 @@ twine==1.12.1
 
 pytest==3.8.2
 pytest-runner==4.2
+certifi>=2023.7.22 # not directly required, pinned by Snyk to avoid a vulnerability
+jinja2>=3.1.3 # not directly required, pinned by Snyk to avoid a vulnerability
+pygments>=2.15.0 # not directly required, pinned by Snyk to avoid a vulnerability
+requests>=2.31.0 # not directly required, pinned by Snyk to avoid a vulnerability