fix typing bug in stocks.py

Fix error in typing which cause the following exception:

File "/home/runner/.cache/huggingface/modules/datasets_modules/datasets/jlh-ibm--earnings_call/012754cae93b94f9282e75f1fcbc0b479228ef5d457509460e0c81633c79acfd/stocks.py", line 10, in StockMarketAnalyzer
market_data: dict[str, pd.DataFrame],

stocks.py

@@ -69,7 +69,7 @@ class StockMarketAnalyzer:
         return stock_ratio > sector_ratio
 
 
-def load_stock_prices(files: Iterable[Path]) -> dict[str, pd.DataFrame]:
+def load_stock_prices(files: Iterable[Path]) -> Dict[str, pd.DataFrame]:
     """
     Load stock prices from CSV files into a dictionary of DataFrames.