Fix incorrect/misleading explanation of duck typing and dynamic typing in the static typing page

[mateuseap]

What I did

• Adjusted a incorrect/misleading explanation of duck typing and dynamic typing in the static typing page. I based myself on what is written on 'Accessing data or logic from an object' section of godot_interfaces.rst tutorial.

Fixes: #7763

[YuriSizov]

I think this needs to be rephrased even further. Also the currently proposed change makes it pointless to use Timer or any other specific type as an example. I think instead of removing the mention of base types they should be incorporated in a different way that supports the point about duck typing.