[V1] Remove additional_config check (#16710)

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm/engine/arg_utils.py

@@ -1361,11 +1361,6 @@ class EngineArgs:
                                recommend_to_remove=True)
             return False
 
-        if self.additional_config != EngineArgs.additional_config:
-            _raise_or_fallback(feature_name="--additional-config",
-                               recommend_to_remove=False)
-            return False
-
         # Xgrammar and Guidance are supported.
         SUPPORTED_GUIDED_DECODING = [
             "xgrammar", "xgrammar:disable-any-whitespace", "guidance",