remove deadlink (#1309)

Author: mszhanyi

beginner_source/dist_overview.rst

@@ -131,8 +131,6 @@ DDP materials are listed below:
    tutorial.
 3. The `Launching and configuring distributed data parallel applications <https://github.com/pytorch/examples/blob/master/distributed/ddp/README.md>`__
    document shows how to use the DDP launching script.
-4. `PyTorch Distributed Trainer with Amazon AWS <aws_distributed_training_tutorial.html>`__
-   demonstrates how to use DDP on AWS.
 
 TorchElastic
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