[drf-flex-field]: Add Support for Django 4.2

[github-actions]

Description

If latest PyPI release does not have Django 4.2 support, then

• Verify if latest master/main branch has support for Django 4.2
• Create issue in the upstream repo for Django 4.2 upgrade if no issue exists already.
• Create pull request in upstream repo for Django 4.2 support if no pull request exists already.
• Fork the repo, Add test configurations for Django 4.0, 4.1 and 4.2 in CI
• Run available django-code-mods to fix the failing tests
• Fix any remaining Django deprecation warnings or test failures in all the test configurations.
• Update the Trove classifiers in any setup.py, setup.cfg, or pyproject.toml files
• Update status in the Dependency Sheet if the package has support for Django 4.2
• Update the repo support field in the Dependency Upgrade Sheet once a new version with support has been released.

[irtazaakram]

I've created upstream PR rsinger86/drf-flex-fields#132.