Simplify GPU install instructions.

[nluehr]

Now that TensorRT is available in the regular CUDA apt repos, the
'machine-learning' repos are no longer needed in the GPU setup instructions.

[kmittman]

Thank you for updating these to use cuda-keyring package to enable the CUDA repository.

[8bitmp3]

Thanks @nluehr !

@mihaimaruseac @MarkDaoust PTAL, thanks!

[markmcd]

Did you mean to remove the TensorRT installation instructions? Have they changed?

The PR description only notes that TensorRT is available elsewhere, I assume it still needs to be installed?

If this section does need to be removed, then the "software requirements" section will need to be updated to remove the "install tensorrt" entry.

[8bitmp3]

Thanks @mihaimaruseac Can you also please check the TensorRT section ?

[nluehr]

The TensorRT installation has been combined with the rest of the CUDA installation (see the libnvinfer* packages) since all packages are now available from a common apt repo.

[markmcd]

Thanks for that info - please update the "software requirements" section to remove the "install tensorrt" entry.

[nluehr]

Instead I added a comment noting that libnvinfer optional and needed for TensorRT.
PTAL.

[markmcd]

@8bitmp3 I've taken a look but it looks like I'm not an owner here so can't actually approve, sorry!