Upgrade edx-exams to Django 4.2

[iamsobanjaved]

Tasks

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1. Add USE_DEPRECATED_PYTZ to the settings, also add pytz to base.in if not there already. (more info: https://docs.djangoproject.com/en/4.2/releases/4.0/#zoneinfo-default-timezone-implementation)
2. Override common constraint of Django
3. Run make upgrade with Django 4.2
4. Drop testing of Django 3.2
5. Inform the owning team about the change in the hashing algorithm (More info: New Hashing Algorithm in Django 4.1 edx-arch-experiments#453)