LibGUI: Remove GModel activations to GAbstractView.

Now you can hook activation via GAbstractView::on_activation.
The design still isn't quite right, we should eventually move the selection
away from the model somehow.

Applications/IRCClient/IRCLogBufferModel.cpp

@@ -72,7 +72,3 @@ void IRCLogBufferModel::update()
 {
     did_update();
 }
-
-void IRCLogBufferModel::activate(const GModelIndex&)
-{
-}