Use torch 2.9 release packages

[GregoryComer]

Summary

Use release 2.9 packages for pytorch and domain libraries in preparation for the final 1.0 release. I'm following the pattern from #13248.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15168

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[mergennachin]

Do you still need these lines?

https://github.com/pytorch/executorch/blob/release/1.0/install_requirements.py#L150-L167

This will be invoked for people install from source in release branch. We should just rely on requirements-examples.txt

[GregoryComer]

CI errors are apparently due to installing the CUDA version of torch. Looking into this now.

CMakeLists.txt:794 (find_package_torch)
  CMake Error at /opt/conda/envs/py_3.10/lib/python3.10/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:90 (message):
    Your installed Caffe2 version uses CUDA but I cannot find the CUDA
    libraries.  Please set the proper CUDA prefixes and / or install CUDA.

Edit: Added index-url back into the install_pytorch.sh script to use cpu variants. Re-testing.

[GregoryComer]

Do you still need these lines?

https://github.com/pytorch/executorch/blob/release/1.0/install_requirements.py#L150-L167

This will be invoked for people install from source in release branch. We should just rely on requirements-examples.txt

Done. Good catch.