Changing operator.div to operator.truediv for Python3 compliance

[bharatagarwal]

I'm not sure whether the intent of the book is to be Python3 compliant or not. However, I noticed in my IDE that operator.div was not available on Python 3.10.

On further digging, I found that Python 3 removed operator.div in favour of two implementations: operator.floordiv and operator.truediv.

Given two integer values, floordiv returns an integer, while truediv returns a float.

My change replaces div with truediv, since that's what the output value 3.0 is indicating.

Reference: https://docs.python.org/3/library/operator.html#mapping-operators-to-functions