fix(modal): remove unused os import

Fixes ruff F401 lint error on modal_cloud.py.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: abrichr

openadapt_ml/cloud/modal_cloud.py

@@ -38,7 +38,6 @@
 
 import argparse
 import json
-import os
 import subprocess
 import sys
 import tempfile