Update data_dir to use environment variable

this was causing an error, because it was set to developer local machine directory

tradingagents/default_config.py

@@ -3,7 +3,7 @@ import os
 DEFAULT_CONFIG = {
     "project_dir": os.path.abspath(os.path.join(os.path.dirname(__file__), ".")),
     "results_dir": os.getenv("TRADINGAGENTS_RESULTS_DIR", "./results"),
-    "data_dir": "/Users/yluo/Documents/Code/ScAI/FR1-data",
+    "data_dir": os.getenv("TRADINGAGENTS_DATA_DIR", "./data"),
     "data_cache_dir": os.path.join(
         os.path.abspath(os.path.join(os.path.dirname(__file__), ".")),
         "dataflows/data_cache",