Update matrix of supported Python versions and remove Cython < 3 tests

[misl6]

This pull request updates the project's Python version support and GitHub Actions workflow to focus on newer Python versions and macOS runners. The changes remove support for older Python versions (3.8, 3.9), add support for Python 3.13 and 3.14, and simplify the Cython configuration in the CI workflow.

Python version and CI workflow updates:

• Updated the GitHub Actions workflow in .github/workflows/python-package.yml to:
  • Remove Python 3.8 and 3.9 from the test matrix and add Python 3.13 and 3.14.
  • Change the macOS runners to use macos-latest and macos-15-intel instead of macos-latest and macos-13.
  • Remove the Cython version matrix and the step that forced a specific Cython version, simplifying dependency management. [1] [2]

Project metadata updates:

• Updated the setup.py classifiers to remove Python 3.8 and 3.9, and add Python 3.13 and 3.14, reflecting the new supported versions.