[LLM] Correct NIXL in docs (ray-project#58258)

## Description

The full name was probably hallucinated from LLM.

## Related issues

## Additional information

Signed-off-by: Rui Qiao <ruisearch42@gmail.com>

Author: ruisearch42

python/ray/llm/_internal/serve/engines/vllm/kv_transfer/nixl.py

@@ -28,7 +28,7 @@ def _set_side_channel_host(self):
     def setup(self) -> None:
         """Initialize the NIXL connector backend.
 
-        This method sets up the NIXL (Network Interface for eXtended LLM) connector by:
+        This method sets up the NIXL (NVIDIA Inference Xfer Library) connector by:
         1. Verifying that the required vLLM environment variables are supported
         2. Configuring the side channel port and host if not already set
         3. Creating a unique engine ID across replicas