Merge pull request #3939 from andrewpollack/update-markdown-py

Bump Python-Markdown 3.3.7

Author: nellshamrell

requirements.txt

@@ -2,7 +2,7 @@ cssmin==0.2.0
 feedgenerator==2.0
 jinja2==2.11.3
 libsass==0.21.0
-Markdown==3.3.6
+Markdown==3.3.7
 markupsafe==2.0.1
 pelican==4.7.1
 pelican-webassets==2.0.0