Update django-cors-headers requirement in /server

Updates the requirements on [django-cors-headers](https://github.com/adamchainz/django-cors-headers) to permit the latest version.
- [Changelog](https://github.com/adamchainz/django-cors-headers/blob/main/CHANGELOG.rst)
- [Commits](adamchainz/django-cors-headers@4.2.0...4.3.0)

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

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

server/requirements.txt

@@ -6,7 +6,7 @@ celery==5.3.*
 channels==4.0.*
 channels_redis==4.1.*
 Django==4.2.*
-django-cors-headers==4.2.*
+django-cors-headers==4.3.*
 django-decorator-include==3.0
 django-extensions==3.2.*
 django-formset-js-improved