fix: Remove unused time import from retraining scheduler

- Removed unused import time from src/automation/retraining_scheduler.py
- time module no longer needed after replacing time.sleep() with event.wait()
- Resolves Ruff F401 error about unused import
- All functionality still works correctly with threading.Event approach

Author: RuiFSP

src/automation/retraining_scheduler.py

@@ -7,7 +7,6 @@
 
 import logging
 import threading
-import time
 from collections.abc import Callable
 from dataclasses import dataclass, field
 from datetime import datetime