[TPU] update torch_xla dependency for PyPI compatibility (#25278)

Signed-off-by: Johnny Yang <johnnyyang@google.com>
Co-authored-by: Chengji Yao <chengjiyao@google.com>

requirements/tpu.txt

@@ -14,14 +14,4 @@ nixl==0.3.0
 tpu_info==0.4.0
 
 # Install torch_xla
---pre
---extra-index-url https://download.pytorch.org/whl/nightly/cpu
+torch_xla[tpu, pallas]==2.8.0
\ No newline at end of file
---find-links https://storage.googleapis.com/libtpu-wheels/index.html
---find-links https://storage.googleapis.com/libtpu-releases/index.html
---find-links https://storage.googleapis.com/jax-releases/jax_nightly_releases.html
---find-links https://storage.googleapis.com/jax-releases/jaxlib_nightly_releases.html
-torch==2.9.0.dev20250730
-torchvision==0.24.0.dev20250730
-torch_xla[tpu, pallas] @ https://storage.googleapis.com/pytorch-xla-releases/wheels/tpuvm/torch_xla-2.9.0.dev20250730-cp311-cp311-linux_x86_64.whl ; python_version == "3.11"
-torch_xla[tpu, pallas] @ https://storage.googleapis.com/pytorch-xla-releases/wheels/tpuvm/torch_xla-2.9.0.dev20250730-cp312-cp312-linux_x86_64.whl ; python_version == "3.12"
-