Bump jinja2 from 2.10 to 2.11.3 in /app

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](pallets/jinja@2.10...2.11.3)

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

Author: dependabot[bot]

app/requirements.txt

@@ -23,7 +23,7 @@ graphql-server-core==1.1.1
 idna==2.8
 inflection==0.3.1
 itsdangerous==1.1.0
-Jinja2==2.10
+Jinja2==2.11.3
 jsonschema==2.6.0
 Mako==1.0.7
 MarkupSafe==1.1.0