remove MPI page from index (#4206)

Co-authored-by: Alex Xu <alex.xu@amd.com>

docs/index.md

@@ -43,7 +43,6 @@ ROCm documentation is organized into the following categories:
 * [System optimization](./how-to/system-optimization/index.rst)
 * [AMD Instinct MI300X performance validation and tuning](./how-to/tuning-guides/mi300x/index.rst)
 * [System debugging](./how-to/system-debugging.md)
-* [Use MPI](./how-to/gpu-enabled-mpi.rst)
 * [Use advanced compiler features](./conceptual/compiler-topics.md)
 * [Set the number of CUs](./how-to/setting-cus)
 * [Troubleshoot BAR access limitation](./how-to/Bar-Memory.rst)