Fix for noise sampling for the TD3 exploration (#260)

Author: dosssman

cleanrl/td3_continuous_action.py

@@ -178,7 +178,7 @@ def forward(self, x):
         else:
             with torch.no_grad():
                 actions = actor(torch.Tensor(obs).to(device))
-                actions += torch.normal(actor.action_bias, actor.action_scale * args.exploration_noise)
+                actions += torch.normal(0, actor.action_scale * args.exploration_noise)
                 actions = actions.cpu().numpy().clip(envs.single_action_space.low, envs.single_action_space.high)
 
         # TRY NOT TO MODIFY: execute the game and log data.