tools: fix Python 3 syntax error in mac_tool.py

PR-URL: https://github.com/nodejs/node/pull/30146


Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>