Ensure consistent spacing in Python.gitignore

[jessijzhao]

Reasons for making this change:

There are currently inconsistent/extraneous spaces in the Python.gitignore. In particular, comments start with 0, 1, 2, or 3 spaces, and the PyCharm description includes a double space.

This commit enforces 1 (for headers/code) or 3 (for descriptions) spaces for comments and removes the extraneous space in the PyCharm description.