build(deps): bump django-cors-headers in /backend/requirements

Bumps [django-cors-headers](https://github.com/adamchainz/django-cors-headers) from 4.2.0 to 4.3.1.
- [Changelog](https://github.com/adamchainz/django-cors-headers/blob/main/CHANGELOG.rst)
- [Commits](adamchainz/django-cors-headers@4.2.0...4.3.1)

---
updated-dependencies:
- dependency-name: django-cors-headers
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/requirements/base.txt

@@ -18,7 +18,7 @@ django-environ==0.11.2 # https://github.com/joke2k/django-environ
 django-celery-beat==2.5.0  # https://github.com/celery/django-celery-beat
 django-extensions==3.2.3  # https://github.com/django-extensions/django-extensions
 drf-spectacular==0.26.5 # https://github.com/tfranzel/drf-spectacular
-django-cors-headers==4.2.0 # https://github.com/adamchainz/django-cors-headers
+django-cors-headers==4.3.1 # https://github.com/adamchainz/django-cors-headers
 
 django-napse==1.10.0 # https://github.com/napse-invest/django-napse
 djangorestframework-api-key==2.3.0