Fix the output file name bug

VidSTG/read_annotation_multithread.py

@@ -36,7 +36,7 @@ def main():
             all_results.extend(future.result())
             progress.update(1)
         
-    with open('results_multithread.json', 'w') as json_file:
+    with open(args.output, 'w') as json_file:
         json.dump(all_results, json_file)