Bump jinja2 from 2.11.1 to 2.11.3 in /src (#79)

Bumps [jinja2](https://github.com/pallets/jinja) from 2.11.1 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@2.11.1...2.11.3)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/requirements.txt

@@ -13,7 +13,7 @@ Flask-WTF==0.14.3
 flake8==3.7.9
 gunicorn==20.0.4
 itsdangerous==1.1.0
-Jinja2==2.11.1
+Jinja2==2.11.3
 MarkupSafe==1.1.1
 psycopg2==2.8.5
 pycparser==2.20