Add test case with final decorator

Author: jairov4

mypyc/test-data/run-dunders.test

@@ -964,4 +964,4 @@ def test_final() -> None:
     assert a + 3 == 8
     assert b + 3 == 9
     assert (a < A(5)) is False
-    assert (a < A(5)) is True
+    assert (b < A(5)) is True