[lint] Ignore shadowing of ord() and chr() builtins in testgen/base58.py

Summary: Ignore A001 since we are explicitly overridding the builtin behavior. Overridding builtins is very hacky but this should be backported out of the code base in the future so it is not worth worrying about.

Test Plan:

flake8 contrib/testgen/base58.py | grep A001  # empty

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D13749