Update Python.gitignore

Add ruff cache. 
ruff tool: https://github.com/charliermarsh/ruff
ruff is becoming a very popular tool often run in pre-commit and aim to replace Flake8 (plus dozens of plugins), isort, pydocstyle, yesqa, eradicate, pyupgrade, and autoflake, all while executing tens or hundreds of times faster than any individual tool.