🧹 [code health improvement] Remove unused sys import in apnea_screener.py

[manupawickramasinghe]

🎯 What: Removed unused sys import in examples/sleep/apnea_screener.py.
💡 Why: The import is unused and removing it improves code cleanliness and maintainability.
✅ Verification: Verified by checking that sys is not used in the code via grep, compiling the python file to ensure no syntax errors were introduced, and passing the code review tool.
✨ Result: The code health issue is resolved without changing behavior.

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PR created automatically by Jules for task 4608971004484567328 started by @manupawickramasinghe

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