fix: doc-site/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-10305723

Author: snyk-bot

doc-site/requirements.txt

@@ -2,3 +2,4 @@ mkdocs-material
 mkdocs-literate-nav
 mkdocs-include-markdown-plugin
 mike
+requests>=2.32.4 # not directly required, pinned by Snyk to avoid a vulnerability