fix: requirements-dev.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-FILELOCK-14458335
- https://snyk.io/vuln/SNYK-PYTHON-PYMDOWNEXTENSIONS-12427119

Author: snyk-bot

requirements-dev.txt

@@ -19,3 +19,5 @@ werkzeug>=3.0.6 # not directly required, pinned by Snyk to avoid a vulnerability
 urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability
 zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability
 requests>=2.32.4 # not directly required, pinned by Snyk to avoid a vulnerability
+filelock>=3.20.1 # not directly required, pinned by Snyk to avoid a vulnerability
+pymdown-extensions>=10.16.1 # not directly required, pinned by Snyk to avoid a vulnerability