test: remove Files: comment processing from Python test runner

We don't use any Files: comments in our tests so remove the Python code
for it from test/testpy/__init__.py.

PR-URL: https://github.com/nodejs/node/pull/25183


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>