S1185: Fix false-positives with "final"

The following example from the documentation did not work, an erroneously reported an issue (and was removed):

class Base {
public:
  void f();
};

class Derived : public Base {
public:
  void f() final { // final
    Base::f();
  }
};

We should handle this case, and update the RSPEC:

Changing the visibility of the function in the derived class or making it final