disable test_setitem_inplace_operator again (#7495)

it was flaky, not broken broken

test/test_setitem.py

@@ -43,6 +43,7 @@ class TestSetitem(unittest.TestCase):
     self.assertFalse(t.lazydata.st.contiguous)
     with self.assertRaises(RuntimeError): t[1] = 5
 
+  @unittest.skip("TODO: flaky")
   def test_setitem_inplace_operator(self):
     t = Tensor.arange(4).reshape(2, 2).contiguous()
     t[1] += 2