Bump jinja2 from 2.10 to 2.11.3

Bumps [jinja2](https://github.com/pallets/jinja) from 2.10 to 2.11.3.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/master/CHANGES.rst)
- [Commits](https://github.com/pallets/jinja/compare/2.10...2.11.3)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -4,6 +4,6 @@ pytz==2018.5
 simplejson==3.16.0
 docutils==0.14
 django-simple-history==2.5.1
-jinja2==2.10
+jinja2==2.11.3
 Sphinx==1.8.4
 django-tex==1.1.7