[python] mod operator is modulus in python, not remainder

[jwunderl]

Describe the bug

mod operator in python is modulus, not remainder; this means it handles negatives differently from javascript.

-1 % 4

in python is 3, in javascript / c++ is -1

To Reproduce
Steps to reproduce the behavior:

1. Go to https://makecode.microbit.org/_LhfXu3iHigXL
2. see console output
3. go to console / terminal window, start python repl (python)
4. print(-1 % 4) in window; see output is different

Expected behavior

Maybe need a helper function for mod to convert to in python or something? It's a bit of an edge case.

Remembered they were different in python when responding to https://forum.makecode.com/t/remainder-modulus-operator-returning-negative-values-when-it-shouldnt/1789