Remove xfail from passing test

tests/tensor/test_extra_ops.py

@@ -329,7 +329,6 @@ class TestDiff(utt.InferShapeTester):
         g = pytensor.function([x], diff(x, n=n, axis=axis))
         assert np.allclose(np.diff(a, n=n, axis=axis), g(a))
 
-    @pytest.mark.xfail(reason="Subtensor shape cannot be inferred correctly")
     @pytest.mark.parametrize(
         "x_type",
         (