Fix broken link to GPU docs (#9023)

Author: ghpvnist

CONTRIBUTING.md

@@ -140,7 +140,7 @@ TorchVision, and PyTorch/XLA.
 
 ### Additional steps for GPU
 
-Please refer to this [guide](https://github.com/pytorch/xla/blob/master/docs/gpu.md#develop-pytorchxla-on-a-gpu-instance-build-pytorchxla-from-source-with-gpu-support).
+Please refer to this [guide](https://github.com/pytorch/xla/blob/master/plugins/cuda/README.md).
 
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