fix relative path and update index.rst

Author: brb-nv

docs/source/features/helix.md

@@ -63,7 +63,7 @@ Please set the following parameters for the generation servers in disaggregated
 
 ### Unit Test: MLA Module Correctness
 
-The simplest correctness test validates the [MLA attention module](../../../../tensorrt_llm/_torch/modules/attention.py) with Helix enabled:
+The simplest correctness test validates the [MLA attention module](../../../tensorrt_llm/_torch/modules/attention.py) with Helix enabled:
 
 ```bash
 # Run the MLA Helix unit test

docs/source/index.rst

@@ -76,6 +76,7 @@ Welcome to TensorRT LLM's Documentation!
    features/auto_deploy/auto-deploy.md
    features/ray-orchestrator.md
    features/torch_compile_and_piecewise_cuda_graph.md
+   features/helix.md
 
 
 .. toctree::