fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-XML2RFC-12668907

Author: snyk-bot

requirements.txt

@@ -81,5 +81,5 @@ tqdm>=4.64.0
 Unidecode>=1.3.4
 urllib3>=1.26,<2
 weasyprint>=64.1
-xml2rfc>=3.23.0
+xml2rfc>=3.30.2
 xym>=0.6,<1.0