modify instance norm en doc (#46817)

python/paddle/nn/functional/norm.py

@@ -382,13 +382,15 @@ def instance_norm(x,
 
     Parameters:
         x(Tensor): Input Tensor. It's data type should be float32, float64.
-        running_mean(Tensor, optional): running mean. Default None.
-        running_var(Tensor, optional): running variance. Default None.
+        running_mean(Tensor, optional): running mean. Default None. Obsolete (that is, no longer usable).
+        running_var(Tensor, optional): running variance. Default None. Obsolete (that is, no longer usable).
         weight(Tensor, optional): The weight tensor of instance_norm. Default: None.
+            If its value is None, this parameter will be initialized by one.
         bias(Tensor, optional): The bias tensor of instance_norm. Default: None.
+            If its value is None, this parameter will be initialized by zero.
         eps(float, optional): A value added to the denominator for numerical stability. Default is 1e-5.
         momentum(float, optional): The value used for the moving_mean and moving_var computation. Default: 0.9.
-        use_input_stats(bool, optional): Default True.
+        use_input_stats(bool, optional): Default True. Obsolete (that is, no longer usable).
         data_format(str, optional): Specify the input data format, may be "NC", "NCL", "NCHW" or "NCDHW". Defalut "NCHW".
         name(str, optional): Name for the InstanceNorm, default is None. For more information, please refer to :ref:`api_guide_Name`..