chore(Snyk): Security upgrade markdown2 from 2.3.9 to 2.4.0 (#12331)

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-MARKDOWN2-1063233

Co-authored-by: snyk-bot <snyk-bot@snyk.io>

requirements.txt

@@ -27,7 +27,7 @@ html5lib==1.0.1
 ipython==7.14.0
 Jinja2==2.11.3
 ldap3==2.7
-markdown2==2.3.9
+markdown2==2.4.0
 maxminddb-geolite2==2018.703
 ndg-httpsclient==0.5.1
 num2words==0.5.10