Retired EOL versions

[zsimic]

List and exercise tests only on py3.9+ (older versions can still be compiled, as the version to build is given explicitly on command line).

~/github/portable-python: .venv/bin/portable-python -q list
cpython:
  3.13: 3.13.2
  3.12: 3.12.9
  3.11: 3.11.11
  3.10: 3.10.16
  3.9: 3.9.21