Update ml-agents/mlagents/trainers/torch/distributions.py

ml-agents/mlagents/trainers/torch/distributions.py

             # throws error on runtime broadcasting due to unknown reason. We
             # use this to replace torch.expand() because it is not supported in
             # the verified version of Barracuda (1.0.X).
-            # log_sigma = mu * 0 + self.log_sigma
             log_sigma = mu * 0 + torch.clamp(self.log_sigma, -20, 2)
         if self.tanh_squash:
             return TanhGaussianDistInstance(mu, torch.exp(log_sigma))