chode(multiple samples) Updating django instances and some of it dependencies.

[XrossFox]

Description

• Django Upgrade: Updated Django to version 6.0.5 (pinned to python_version >= "3.12") across App Engine, Cloud Run, and Kubernetes Engine samples. Removed all outdated conditional dependencies for older
  Django versions (3.x, 4.x, 5.x).
• Dependency Bumps:
  • Upgraded django-environ from 0.10.0/0.12.0 to 0.13.0.
  • Upgraded pytest-django from 4.9.0 to 4.12.0 in all requirements-test.txt files.
  • Cleaned up redundant gunicorn Python 2 entries in kubernetes_engine/django_tutorial/requirements.txt.
• Nox Configuration Updates: Modified noxfile_config.py across 7 Django samples to update the ignored_versions list. Python 3.8, 3.9, 3.10, 3.11, and 3.13 are now explicitly ignored for testing, aligning
  tests with the new Django 6.x requirements.

Note: run/django is not working properly, this is a known bug documented in b/479621565

Fixes b/511192727

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request attempts to update dependencies across several projects, including Django, django-environ, and pytest-django. The reviewer identified that the requested versions (Django 6.0.5, django-environ 0.13.0, and pytest-django 4.12.0) are not valid releases on PyPI and suggests reverting to the latest stable versions (Django 5.1.6, django-environ 0.12.0, and pytest-django 4.10.0) while maintaining compatibility with supported Python runtimes.

[XrossFox]

Code Review

This pull request attempts to update dependencies across several projects, including Django, django-environ, and pytest-django. The reviewer identified that the requested versions (Django 6.0.5, django-environ 0.13.0, and pytest-django 4.12.0) are not valid releases on PyPI and suggests reverting to the latest stable versions (Django 5.1.6, django-environ 0.12.0, and pytest-django 4.10.0) while maintaining compatibility with supported Python runtimes.

This is not true at all, i've checked existence directly in Pypi. The point of this PR is to update to secure versions of Django (6.0.5), which no longer support any python release under 3.12.

[Kef131]

lgtm