Fix incorrect docstring for stop_profile() method (#27101)

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

vllm/engine/protocol.py

@@ -110,7 +110,7 @@ class EngineClient(ABC):
 
     @abstractmethod
     async def stop_profile(self) -> None:
-        """Start profiling the engine"""
+        """Stop profiling the engine"""
         ...
 
     @abstractmethod