Bump django from 2.2.27 to 2.2.28

Bumps [django](https://github.com/django/django) from 2.2.27 to 2.2.28.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.2.27...2.2.28)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -6,7 +6,7 @@ bz2file==0.98
 certifi==2018.10.15
 chardet==3.0.4
 cycler==0.10.0
-Django==2.2.27
+Django==2.2.28
 django-extensions==2.1.3
 docutils==0.14
 gensim==3.6.0