Remove triton. (#9601)

This PR removes all triton code (e.g. test and implementation) from the
Pytorch/XLA codebase. This is in line with the CUDA deprecation that
started on release 2.8.

**Key Changes:**

- (`docs/source/features/triton.md`) Remove the documentation
- (`test/test_triton.py`) Remove the triton tests
- (`torch_xla/experimental/triton.py`) Remove the triton implementation

Author: ysiraichi

README.md

@@ -97,7 +97,7 @@ Our github contains many useful docs on working with different aspects of PyTorc
 - [docs/source/learn](https://github.com/pytorch/xla/tree/master/docs/source/learn): docs for learning concepts associated with XLA, troubleshooting, pjrt, eager mode, and dynamic shape.
 - [docs/source/accelerators](https://github.com/pytorch/xla/tree/master/docs/source/accelerators): references to `GPU` and `TPU` accelerator documents.
 - [docs/source/perf](https://github.com/pytorch/xla/tree/master/docs/source/perf): documentation about performance specific aspects of PyTorch/XLA such as: `AMP`, `DDP`, `Dynamo`, Fori loop, `FSDP`, quantization, recompilation, and `SPMD`
-- [docs/source/features](https://github.com/pytorch/xla/tree/master/docs/source/features): documentation on distributed torch, pallas, scan, stable hlo, and triton.
+- [docs/source/features](https://github.com/pytorch/xla/tree/master/docs/source/features): documentation on distributed torch, pallas, scan, and stable hlo.
 - [docs/source/contribute](https://github.com/pytorch/xla/tree/master/docs/source/contribute): documents on setting up PyTorch for development, and guides for lowering operations.
 - PJRT plugins:
   - [CPU](https://github.com/pytorch/xla/blob/master/plugins/cpu/README.md)

docs/source/features/triton.md

@@ -90,7 +90,6 @@ Tutorials
    :caption: Training on GPU
 
    accelerators/gpu
-   features/triton
    perf/spmd_gpu
 
 .. toctree::