[Bugfix] when use s3 model cannot use default load_format (#24435)

Signed-off-by: rongfu.leng <rongfu.leng@daocloud.io>
Co-authored-by: 22quinn <33176974+22quinn@users.noreply.github.com>

vllm/engine/arg_utils.py

@@ -959,7 +959,6 @@ class EngineArgs:
         if (not isinstance(self, AsyncEngineArgs) and envs.VLLM_CI_USE_S3
                 and self.model in MODELS_ON_S3 and self.load_format == "auto"):
             self.model = f"{MODEL_WEIGHTS_S3_BUCKET}/{self.model}"
-            self.load_format = "runai_streamer"
 
         if self.disable_mm_preprocessor_cache:
             logger.warning(