Add support for Django 4.2 in enterprise-subsidy

[iamsobanjaved]

In order to have support for Django 4.2, we first need to run tests on Django 4.2 in the entrerprise-subsidy service. For updating CI, we should run tox and GitHub actions modernizers.

Tox Modernizer: tox_moderniser_django42.py

Github Action Modernizer: github_actions_modernizer_django42.py

### A/C
- [ ] Fix Django 4.0 and 4.1 removal warnings
- [ ] Run tests with Django 4.2
- [ ] Fix all test failures with Django 4.2 (if any)
- [ ] After merging, ask the owning squad to add Django 4.2 tests in branch protection rules

After completion kindly unblock this: Arbi-BOM (view)