Drop django42 support across openedx packages.

[awais786]

Django 5.2 has been merged successfully.

Now is the right time to remove Django 4.2 from our tests.

Steps:

1. Remove Django 4.2 from both tox and GitHub Actions.
2. Run make upgrade using Django 5.2.
3. Remove Django 4.2 from the package classifiers.
4. Bump the version and create a new release.

Sample PR

[awais786]

@feanil I will ask my team members to start working on this.

[feanil]

@awais786 thanks! If you list all the PRs here I can help shepherd any that need reviews.

[feanil]

Also, if you ticket up the work for each repo the Maintainers of those repos should be able to take on this work as well.