Bump django from 2.1.11 to 2.2.24

Bumps [django](https://github.com/django/django) from 2.1.11 to 2.2.24.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.1.11...2.2.24)

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

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

requirements.txt

@@ -1,4 +1,4 @@
-django==2.1.11
+django==2.2.24
 pytest==3.8.2
 pytest-cov==2.6.0
 pytest-django==3.4.3