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

@@ -9,7 +9,7 @@ Flask-MySQL==1.4.0
 gunicorn==19.9.0
 idna==2.7
 itsdangerous==0.24
-Jinja2==2.10
+Jinja2==2.11.3
 MarkupSafe==1.0
 mysqlclient==1.3.13
 pycparser==2.18