fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-1012994

requirements.txt

@@ -10,7 +10,7 @@
 # `Pipfile.lock` and then regenerate `requirements*.txt`.
 ################################################################################
 
-jinja2==2.11.1
+jinja2==2.11.3
 markupsafe==1.1.1
 pendulum==1.5.1
 python-dateutil==2.8.1