Update Python.gitignore for PEP 441

[hspaans]

PEP 441 introduces Python ZIP Applications to bundle a Python Application into a ZIP file with file extension pyz.

Reasons for making this change: Python ZIP Applications, described in PIP 441, are an artifact from the build process and shouldn't be added to the repository. These files have their own file extension pyz making it easy to exclude them.

Links to documentation supporting these rule changes:

• PEP 441 describing Python ZIP Applications