!1896 fix lars weight decay computation error

Merge pull request !1896 from gziyan/fix_lars_weight_decay

mindspore/nn/optim/lars.py

@@ -94,7 +94,7 @@ class LARS(Optimizer):
         self.learning_rate = optimizer.learning_rate
         self.lars = P.LARSUpdate(epsilon, hyperpara, use_clip)
         self.reciprocal_scale = 1.0 / loss_scale
-        self.weight_decay = weight_decay * loss_scale
+        self.weight_decay = weight_decay
         self.cast = P.Cast()
         self.decay_flag = tuple(decay_filter(x) for x in self.parameters)
         self.lars_flag = tuple(lars_filter(x) for x in self.parameters)