Update dependency markdown2 to v2.3.9 (#237)

Co-authored-by: Renovate Bot <bot@renovateapp.com>
Co-authored-by: Ahmed <hello@clivern.com>

Author: 3 people

requirements.txt

@@ -8,7 +8,7 @@ jsonschema==3.2.0
 celery==4.4.2
 redis==3.5.2
 cryptography==2.9.2
-markdown2==2.3.8
+markdown2==2.3.9
 twilio==6.40.0
 pyumetric==0.0.4
 pyvalitron==1.1.3