MNT Fix broken test

Author: DimitriPapadopoulos

numpy/_core/tests/test_ufunc.py

@@ -495,7 +495,7 @@ def test_signature_dtype_instances_allowed(self, get_kwarg):
         assert int64 is not int64_2
 
         assert np.add(1, 2, **get_kwarg(int64_2)).dtype == int64
-        td = np.timedelta(2, "s")
+        td = np.timedelta64(2, "s")
         assert np.add(td, td, **get_kwarg("m8")).dtype == "m8[s]"
 
         msg = "The `dtype` and `signature` arguments to ufuncs"