doc: remove a note about functor-based connection complexity for overloads

What we had initially:

connect(slider, &QSlider::valueChanged,
        lcd, static_cast<void (QLCDNumber::*)(int)>(&QLCDNumber::display));

was more complex than string-based solution:

connect(slider, SIGNAL(valueChanged(int)),
        lcd, SLOT(display(int)));

But since Qt 5.7 we have qOverload/QOverload:

connect(slider, &QSlider::valueChanged,
        lcd, QOverload<int>::of(&QLCDNumber::display));

connect(slider, &QSlider::valueChanged,
        lcd, qOverload<int>(&QLCDNumber::display));

Which is not complex at all, just a bit different to what Qt developers
are used to.

Task-number: QTBUG-63297
Change-Id: I49f7bf228812ceadc38c601d8a711fd250216b52
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

doc/src/signalslotsyntaxes.qdoc

@@ -61,10 +61,6 @@ The table below summarizes their differences.
     \li Can connect C++ functions to QML functions
     \li Y
     \li
-\row
-    \li Selecting an instance of an overloaded signal or slot is...
-    \li Simple
-    \li Complex
 \endtable
 
 The following sections explain these differences in detail and demonstrate how