text: Title: Why there is no square root at area_temperature?
  Body: https://github.com/tensorflow/tensor2tensor/blob/5623deb79cfcd28f8f8c5463b58b5bd76a81fd0d/tensor2tensor/layers/area_attention.py#L415
  
  In typical dot product attention, logit which is the input matrix of softmax supposed to be divided by square rooted temperature like the equation below.
  ![image](https://user-images.githubusercontent.com/63258184/140316988-7c87e78f-0ad8-415d-a860-8d751c124cb0.png)
  
  However, in this code, logit is just divided with temperature without a square root. Is it correct or wrong? If it is correct, could you explain why you didn't add square root?