Remove sweep_log prefix from json progress bar

fairseq/progress_bar.py

@@ -118,7 +118,7 @@ class json_progress_bar(progress_bar):
     def print(self, stats):
         """Print end-of-epoch stats."""
         stats = self._format_stats(self.stats, epoch=self.epoch)
-        print("sweep_log: " + json.dumps(stats), flush=True)
+        print(json.dumps(stats), flush=True)
 
     def _format_stats(self, stats, epoch=None, update=None):
         postfix = OrderedDict()