Bump django from 1.11.23 to 2.2.24 in /requirements

Bumps [django](https://github.com/django/django) from 1.11.23 to 2.2.24.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@1.11.23...2.2.24)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
...

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

requirements/test.txt

@@ -1,6 +1,6 @@
 coverage==4.5.3
 coveralls==1.8.0
-Django==1.11.23
+Django==2.2.24
 docopt==0.6.2
 flake8==3.7.7
 mccabe==0.6.1