[Refactor] Remove legacy --stage-configs-path from the serve CLI (#5647)

Signed-off-by: zwhzzz0821 <2831474076@qq.com>

docs/design/qwen3_omni_tts_performance_optimization.md

@@ -419,8 +419,7 @@ Notes:
 ```bash
 vllm serve Qwen/Qwen3-Omni-30B-A3B-Instruct \
   --omni \
-  --port 8091 \
-  --stage-configs-path vllm_omni/model_executor/stage_configs/qwen3_omni_moe_async_chunk.yaml
+  --port 8091
 ```
 
 #### 3) Key config knobs
@@ -494,7 +493,7 @@ The default config (`qwen3_tts.yaml`) enables the full optimization stack:
 vllm-omni serve Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice \
   --omni \
   --port 8000 \
-  --stage-configs-path vllm_omni/model_executor/stage_configs/qwen3_tts_no_async_chunk.yaml
+  --no-async-chunk
 ```
 
 #### 3) Key config knobs