Don't handle QEvent::Hide anymore

Update the buttons in DockWidget::setIsOpen() instead.
This makes the controllers self-contained and not depending
on the "view technology". Other frameworks might not even
have the concept of show/hidden events

src/controllers/DockWidget.cpp

@@ -866,21 +866,12 @@ void DockWidget::Private::onParentChanged()
 
 void DockWidget::onShown()
 {
-    d->updateToggleAction();
-    d->updateFloatAction();
-
     d->maybeRestoreToPreviousPosition();
 
     // Transform into a FloatingWindow if this will be a regular floating dock widget.
     QTimer::singleShot(0, d, &DockWidget::Private::maybeMorphIntoFloatingWindow);
 }
 
-void DockWidget::onHidden()
-{
-    d->updateToggleAction();
-    d->updateFloatAction();
-}
-
 void DockWidget::onResize(QSize)
 {
     if (isOverlayed()) {
@@ -1069,4 +1060,7 @@ void DockWidget::Private::setIsOpen(bool is)
         close();
 
     m_isOpen = is;
+
+    updateToggleAction();
+    updateFloatAction();
 }