Bump django from 2.2.7 to 2.2.28 in /cat_db

Bumps [django](https://github.com/django/django) from 2.2.7 to 2.2.28.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.2.7...2.2.28)

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

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

cat_db/requirements.txt

@@ -1,4 +1,4 @@
-django == 2.2.7
+django == 2.2.28
 djangorestframework == 3.10.3
 factory_boy == 2.12.0
 django-debug-toolbar == 2.1