typo in neural net

doc/src/NeuralNet/NeuralNet.do.txt

@@ -2263,7 +2263,7 @@ since the gradient of the ReLU function is 0 when its input is negative.
 To solve this problem, you may want to use a variant of the ReLU function, such as the leaky ReLU discussed before or the so-called exponential linear unit (ELU) function
 !bt
 \[
-ELU(z) = \left\{\begin{array}{cc} \alpha\left( \exp{(z)}-1\right) & z > 0,\\  z & z \le 0.\end{array}\right. 
+ELU(z) = \left\{\begin{array}{cc} \alpha\left( \exp{(z)}-1\right) & z < 0,\\  z & z \ge 0.\end{array}\right. 
 \]
 !et