Update supported Django/Python versions and drop EOL versions

[jasongi]

I was doing the update for collectfasta and thought I'd raise an issue here to update the package as I noticed it was unsupported in the cookiecutter-django 6.0 issue.

Here's a summary of the changes to bring us up to date:

- Django 6.0 is out - add support
- Django 5.0, 5.1 are EOL - drop support
- Python 3.8/3.9 are EOL - drop support
- Python 3.13 and 3.14 are supported by 5.2 and 6.0 - add support

I'm going to try raise a PR for this today.