bpo-29710: Clarify documentation for Bitwise binary operation (GH-1691)

bpo-29710: Clarify documentation for Bitwise binary operation (GH-1691)

Mathematically, bitwise operations on integers behave as if there were an
infinite number of sign bits. Pragmatically, that gives the same answer as
using one extra sign bit for the bitwise logical operations.
(cherry picked from commit b4bc5cab82e6855e4ebc33ba0b669ddffad30fb3)

Co-authored-by: Sanyam Khurana <8039608+CuriousLearner@users.noreply.github.com>