Remove whitespaces before colons in pythondemo.py
This is the more common syntax and it is PEP 8 compliant.
Although PEP default indentation width is 4, the default indentation width of TIC-80 is 1, so this commit changes it to 1. As is typical for TIC-80's brevity, this commit removes spaces after commas as well.
https://peps.python.org/pep-0008/