Bump django from 2.2.6 to 2.2.8

Bumps [django](https://github.com/django/django) from 2.2.6 to 2.2.8.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.2.6...2.2.8)

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

requirements.txt

@@ -1,6 +1,6 @@
 certifi==2019.3.9
 chardet==3.0.4
-Django==2.2.6
+Django==2.2.8
 django-background-tasks==1.2.0
 django-ratelimit==2.0.0
 ecdsa>=0.13.3