Fix the log to correct guide user to install modelscope (#9793)

Signed-off-by: yuze.zyz <yuze.zyz@alibaba-inc.com>

vllm/transformers_utils/__init__.py

@@ -9,7 +9,7 @@ if VLLM_USE_MODELSCOPE:
     if version.parse(modelscope.__version__) <= version.parse('1.18.0'):
         raise ImportError(
             'Using vLLM with ModelScope needs modelscope>=1.18.1, please '
-            'install by `pip install modelscope>=1.18.1`')
+            'install by `pip install modelscope -U`')
 
     from modelscope.utils.hf_util import patch_hub