chore: fix flake8 error in CI

Author: SunsetWolf

qlib/contrib/strategy/signal_strategy.py

@@ -619,9 +619,6 @@ def get_last_n(li, n):
             def filter_stock(li):
                 return li
 
-        # Use instance configuration; keep behavior unchanged (no external kwargs expected here)
-        risk_aversion = copy.deepcopy(getattr(self, "risk_aversion", None))
-
         current_temp: Position = copy.deepcopy(self.trade_position)
 
         # Build current long/short lists by sign of amount