Revert "LibGUI: Only dispatch Leave if the now-hovered widget isn't a child"

This reverts commit cfc9ee6f16b9c4d2b246bb2832dd436637cbeaad.

This change was wrong: The parent *does* lose hover when the mouse
cursor enters a child widget. Hover is not hierarchical, there is only a
hovered window and a hovered widget within that window.

This fixes an issue with GUI::TabWidget buttons appearing hovered
despite the mouse cursor not being over the buttons.

Userland/Libraries/LibGUI/Widget.cpp

@@ -1143,20 +1143,4 @@ bool Widget::is_visible_for_timer_purposes() const
     return is_visible() && Object::is_visible_for_timer_purposes();
 }
 
-bool Widget::is_parent_of(Widget const* widget) const
-{
-    if (widget == nullptr)
-        return false;
-
-    Widget const* current_widget = widget->parent_widget();
-
-    while (current_widget != nullptr) {
-        if (current_widget == this)
-            return true;
-        current_widget = current_widget->parent_widget();
-    }
-
-    return false;
-}
-
 }

Userland/Libraries/LibGUI/Widget.h

@@ -280,8 +280,6 @@ public:
 
     bool has_pending_drop() const;
 
-    bool is_parent_of(Widget const*) const;
-
 protected:
     Widget();
 

Userland/Libraries/LibGUI/Window.cpp

@@ -802,7 +802,7 @@ void Window::set_hovered_widget(Widget* widget)
     if (widget == m_hovered_widget)
         return;
 
-    if (m_hovered_widget && !m_hovered_widget->is_parent_of(widget))
+    if (m_hovered_widget)
         Core::EventLoop::current().post_event(*m_hovered_widget, make<Event>(Event::Leave));
 
     m_hovered_widget = widget;