!28467 fix formula issue I4OSPR

Merge pull request !28467 from yingchen/code_docs_ops

docs/api/api_python/ops/mindspore.ops.Sigmoid.rst

@@ -9,7 +9,7 @@ mindspore.ops.Sigmoid
 
     .. math::
 
-        \text{sigmoid}(x_i) = \frac{1}{1 + \exp(-x_i)},
+        \text{sigmoid}(x_i) = \frac{1}{1 + \exp(-x_i)}
 
     其中， :math:`x_i` 是输入Tensor的一个元素。
 

mindspore/python/mindspore/ops/operations/nn_ops.py

@@ -828,7 +828,7 @@ class Sigmoid(Primitive):
 
     .. math::
 
-        \text{sigmoid}(x_i) = \frac{1}{1 + \exp(-x_i)},
+        \text{sigmoid}(x_i) = \frac{1}{1 + \exp(-x_i)}
 
     where :math:`x_i` is an element of the input Tensor.