Replace pytorch-gpu with pytorch in environment.yml

[ashnair1]

Fixes #293

Tried this on my Linux machine and it installs pytorch 1.10.0 with gpu support.

[ashnair1]

Should we add a note regarding the windows situation? You can't use environment.yml to create an environment on windows due to pytorch and torchvision (from conda-forge) and pycocotools not supporting it.

[adamjstewart]

Yeah, we should probably add a note for Windows. Spack also doesn't yet support Windows, although that's a work in progress. Idk how many of our users actually use Windows.

[calebrob6]

Works for me too!

It looks like conda-forge has:

• pytorch
• pytorch-cpu
• pytorch-gpu

the "pytorch" version has both cpu and cuda versions -- https://anaconda.org/conda-forge/pytorch/files?version=1.10.0 -- I'm not sure how conda install selects between them, but I think it should be fine.

[remtav]

Yeah, we should probably add a note for Windows. Spack also doesn't yet support Windows, although that's a work in progress. Idk how many of our users actually use Windows.

See issue #527