chore: drop Django 4.2 support

[aznszn]

Description: Dropped Django 4.2 support. Removed Django 4.2 from CI matrix, tox environments, and setup.py classifiers.

Issue: openedx/public-engineering#458

JIRA: N/A

Dependencies: N/A

Merge deadline: N/A

Installation instructions: N/A

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• tag reviewer
• tag reviewer

Merge checklist:

• All reviewers approved
• CI build is green
• Version bumped
• Changelog record added
• Documentation updated (not only docstrings)
• Commits are squashed

Post merge:

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• Create a new release (can be done here https://github.com/edx/edx-ace/releases)
• Check new version is pushed to PyPI after tag-triggered build is finished.
• Delete working branch (if not needed anymore)

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[Copilot]

Pull request overview

This PR removes Django 4.2 as a supported/tested framework version for the project, updating CI, tox environments, and package metadata accordingly.

Changes:

• Removed the Django 4.2 tox factor/env and CI job entry, leaving Django 5.2 as the tested Django version.
• Updated package classifiers to no longer advertise Django 4.2 support.
• Added a changelog entry noting the support drop.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tox.ini	Removes django42 factor and narrows the envlist to Django 5.2.
.github/workflows/ci.yml	Drops django42 from the GitHub Actions matrix.
setup.py	Removes the Framework :: Django :: 4.2 classifier.
CHANGELOG.rst	Documents the removal of Django 4.2 support under Unreleased.

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[Copilot]

The tox envlist defines a single Django test environment named py312-django52, but the CI workflow matrix uses TOXENV=django52. django52 is not a defined tox environment in this repo (no [testenv:django52]), so tox will error in CI. Align the env naming by either updating envlist/adding a django52 env, or updating CI to run py312-django52.

[aznszn]

addressed in 3ec662e

[Copilot]

The workflow matrix uses toxenv: ... django52, but tox.ini doesn't define a django52 environment (it defines py312-django52). With TOXENV=django52, tox will fail due to an unknown environment. Align the matrix value with the tox env name (and update the later coverage if that checks matrix.toxenv=='django52' accordingly), or add a matching django52 tox env.

[Copilot]

This PR drops Django 4.2 support and the package classifiers now only advertise Django 5.2, but install_requires is still loaded from requirements/base.in, which currently allows Django>=2.2. That means pip can install this project alongside unsupported Django versions despite the advertised support. Consider updating the Django requirement (in requirements/base.in and/or via constraints) to enforce the minimum supported Django version for releases that drop 4.2.