Update link and installation instructions for cuDNN 7.6.4 for CUDA 10.1

Point to cuDNN archive that contains cuDNN 7.6.4 for CUDA 10.1 and include necessary cuDNN installation instructions.

Fixes issue dotnet#43972 and non-precise doc introduced by PR dotnet#44444

Author: thomasclaudiushuber

docs/machine-learning/how-to-guides/install-gpu-model-builder.md

@@ -27,7 +27,7 @@ Learn how to install the GPU drivers to use your GPU with Model Builder.
 - NVIDIA developer account. If you don't have one, [create a free account](https://developer.nvidia.com/developer-program).
 - Install dependencies:
   - Install [CUDA v10.1](https://developer.nvidia.com/cuda-10.1-download-archive-update2). Make sure you install CUDA v10.1, not any other newer version.
-  - Install [cuDNN for CUDA 10.1](https://developer.nvidia.com/rdp/cudnn-download). (You can't have multiple versions of cuDNN installed.)
+  - Install [cuDNN v7.6.4 for CUDA 10.1](https://developer.nvidia.com/rdp/cudnn-archive) from the cuDNN archive. You cannot have multiple versions of cuDNN installed. After downloading cuDNN v7.6.4 zip file and unpacking it, copy `<CUDNN_zip_files_path>\cuda\bin\cudnn64_7.dll` to `<YOUR_DRIVE>\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v10.1\bin`.
 
 ## Troubleshooting