[CI/Build] Fix plugin tests (#21758)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/models/test_oot_registration.py

@@ -15,13 +15,10 @@ def test_plugin(
     monkeypatch: pytest.MonkeyPatch,
     dummy_opt_path: str,
 ):
-    # V1 shuts down rather than raising an error here.
     with monkeypatch.context() as m:
-        m.setenv("VLLM_USE_V1", "0")
         m.setenv("VLLM_PLUGINS", "")
 
-        match = "Cannot find model module"
-        with pytest.raises(ValueError, match=match):
+        with pytest.raises(ValueError, match="are not supported for now"):
             LLM(model=dummy_opt_path, load_format="dummy")