tools: fix Python 3 deprecation warning in test.py

PR-URL: https://github.com/nodejs/node/pull/30208


Reviewed-By: Christian Clauss <cclauss@me.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>