Bump django from 3.2.9 to 4.0

Bumps [django](https://github.com/django/django) from 3.2.9 to 4.0.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.2.9...4.0)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

config/requirements_core.txt

@@ -1,7 +1,7 @@
 # The necessary dependencies to run Tabbycat
 
 # Django
-Django==3.2.9
+Django==4.0
 django-appconf==1.0.4                   # Helper for handling app configs
 django-better-admin-arrayfield==1.4.2   # Admin widget for ArrayField
 django-dynamic-preferences==1.10.1      # Settings management