[lint] Fix variables shadowing python builtins in zmq_sub.py

Summary: Shadowing builtins can lead to unexpected behavior. Continuing work from D13740

Test Plan:

ninja bitcoind
./src/bitcoind -testnet -zmqpubsequence=tcp://127.0.0.1:28332
../contrib/zmq/zmq_sub.py

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D13750