explictly del df to fix oom

utils/swe_bench.py

@@ -176,6 +176,7 @@ def agg_stats(df):
 def get_resolved_stats_from_filepath(filepath):
     df = load_df_from_selected_filepaths(filepath)
     stats = agg_stats(df)
+    del df
     if not len(stats):
         return {
             'success_rate': None,