Remove tpuvm dependency from r2.4 branch

[will-cromar]

Otherwise we get this error:

ERROR    HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/        
         Can't have direct dependency: libtpu-nightly@                          
         https://storage.googleapis.com/cloud-tpu-tpuvm-artifacts/wheels/libtpu-
         nightly/libtpu_nightly-0.1.dev20240612-py3-none-any.whl ; extra ==     
         "tpuvm". See https://packaging.python.org/specifications/core-metadata 
         for more information. 

[will-cromar]

@JackCaoG what do you think of just removing this dep on master too? We'll have to update any tests/usage that uses torch_xla[tpuvm] to use torch_xla[tpu] -f ...

[JackCaoG]

I forgot why we switched to tpu from tpuvm but if this is the future direction we should just deprecate old usage.. only thing I am not sure if can we add some warning messages when users run with [tpuvm]

[will-cromar]

PyPI rejecting the tpuvm form (direct dependency on HTTP URL) is the reason we added tpu instead. FWIW, tpuvm has not been in stable releases since 2.1.0 for exactly this reason. This would only affect us and potentially any users of the nightly package.