remove deprecated code from old multi-screens arch

--Latte will no longer try to be too smart concerning
the multi-screens behavior. At the old implementation
Latte wouldnt let you reach at a state that you dont
have a tasks plasmoid available. Such a case could be
when the user moves a dock from primary to explicit
screen and disables the screen afterwards. That case
should be thought better in the future in order to be
identified and handled properly without making the
code unnecessary complex. Such an example could be by
identifing the case and asking the user for actions.

(cherry picked from commit b2f1f98b57)

app/dock/dockview.cpp

@@ -490,14 +490,9 @@ void DockView::reconsiderScreen()
 
     qDebug() << "dock screen exists  ::: " << screenExists;
 
-    int docksWithTasks = m_managedLayout ? m_managedLayout->noDocksWithTasks() : 0;
-
     //! 1.a primary dock must be always on the primary screen
-    //! 2.the last tasks dock must also always on the primary screen
-    //! even though it has been configured as an explicit
-    if ((m_onPrimary || (tasksPresent() && docksWithTasks == 1 && !screenExists))
-        && (m_screenToFollowId != qGuiApp->primaryScreen()->name()
-            || m_screenToFollow != qGuiApp->primaryScreen())) {
+    if (m_onPrimary && (m_screenToFollowId != qGuiApp->primaryScreen()->name()
+                        || m_screenToFollow != qGuiApp->primaryScreen())) {
         using Plasma::Types;
         QList<Types::Location> edges{Types::BottomEdge, Types::LeftEdge,
                                      Types::TopEdge, Types::RightEdge};
@@ -510,25 +505,18 @@ void DockView::reconsiderScreen()
         qDebug() << "dock location:" << location();
 
         if (edges.contains(location())) {
-            //! case 2
-            if (!m_onPrimary && !screenExists && tasksPresent() && (docksWithTasks == 1)) {
-                qDebug() << "reached case 2 of updating dock primary screen...";
-                setScreenToFollow(qGuiApp->primaryScreen(), false);
-            } else {
-                //! case 1
-                qDebug() << "reached case 1 of updating dock primary screen...";
-                setScreenToFollow(qGuiApp->primaryScreen());
-            }
-
+            //! case 1
+            qDebug() << "reached case 1: of updating dock primary screen...";
+            setScreenToFollow(qGuiApp->primaryScreen());
             syncGeometry();
         }
     } else if (!m_onPrimary) {
-        //! 3.an explicit dock must be always on the correct associated screen
+        //! 2.an explicit dock must be always on the correct associated screen
         //! there are cases that window manager misplaces the dock, this function
         //! ensures that this dock will return at its correct screen
         foreach (auto scr, qGuiApp->screens()) {
             if (scr && scr->name() == m_screenToFollowId) {
-                qDebug() << "updating the explicit screen for dock...";
+                qDebug() << "reached case 2: updating the explicit screen for dock...";
                 setScreenToFollow(scr);
                 syncGeometry();
                 break;