[doc] improve readability (#18675)

Signed-off-by: reidliu41 <reid201711@gmail.com>
Co-authored-by: reidliu41 <reid201711@gmail.com>

docs/features/spec_decode.md

@@ -45,8 +45,13 @@ for output in outputs:
 To perform the same with an online mode launch the server:
 
 ```bash
-python -m vllm.entrypoints.openai.api_server --host 0.0.0.0 --port 8000 --model facebook/opt-6.7b \
-    --seed 42 -tp 1 --gpu_memory_utilization 0.8 \
+python -m vllm.entrypoints.openai.api_server \
+    --host 0.0.0.0 \
+    --port 8000 \
+    --model facebook/opt-6.7b \
+    --seed 42 \
+    -tp 1 \
+    --gpu_memory_utilization 0.8 \
     --speculative_config '{"model": "facebook/opt-125m", "num_speculative_tokens": 5}'
 ```