!8085 Loss saved does not reduce precision in SummaryCollector

Merge pull request !8085 from ougongchang/fix_round

mindspore/train/callback/_summary_collector.py

@@ -548,8 +548,7 @@ class SummaryCollector(Callback):
         if not isinstance(loss, Tensor):
             loss = Tensor(loss)
 
-        precision = 4
+        loss = Tensor(np.mean(loss.asnumpy()))
-        loss = Tensor(round(np.mean(loss.asnumpy()), precision))
         return loss
 
     def _get_optimizer(self, cb_params):