Adapt the integration code to un-nested inputs

Author: mbegel

tests/integration/test_integration.py

@@ -658,14 +658,6 @@ def f(i):
 
         pytest.fail("extra output nesting")
 
-    with pytest.raises(IncorrectTypeException):
-
-        @app.callback(Output("out", "children"), Input("in", "children"))
-        def f2(i):
-            return i
-
-        pytest.fail("un-nested input")
-
     with pytest.raises(IncorrectTypeException):
 
         @app.callback(