Chore: drop unused isfile import from wasm isolate script

[Doryu001]

Remove the unused isfile import and the obsolete pylint suppression from scripts/wasm-rebuild/docker-scripts/isolate_tests.py keep the required join helper so the script’s filesystem traversal remains intact let tooling surface genuine dead-import issues instead of hiding them behind suppressions

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[clonker]

I tried very hard to find a place where this is used, especially with the comment indicating that that is the case, in fact. But alas, couldn't find anything and you are absolutely right, imo such warnings shouldn't be suppressed. Thanks!