Remove "Critical always on top" notification option

There is no conceivable use case for turning this off, and the UI is
being removed in https://invent.kde.org/plasma/plasma-desktop/-/merge_requests/447.

So let's remove the backend code too, or else anyone who for some reason
had turned it off would be left without a GUI method of turning it back
on again.

applets/notifications/package/contents/ui/global/Globals.qml

@@ -456,7 +456,7 @@ QtObject {
             readonly property var notificationId: model.notificationId
 
             popupWidth: globals.popupWidth
-            type: (model.urgency === NotificationManager.Notifications.CriticalUrgency && notificationSettings.keepCriticalAlwaysOnTop)
+            type: model.urgency === NotificationManager.Notifications.CriticalUrgency
                   || (model.urgency === NotificationManager.Notifications.NormalUrgency && notificationSettings.keepNormalAlwaysOnTop)
                   ? PlasmaCore.Dialog.CriticalNotification : PlasmaCore.Dialog.Notification
 

libnotificationmanager/kcfg/notificationsettings.kcfg

@@ -9,9 +9,6 @@
         <entry name="CriticalInDndMode" type="Bool">
             <default>true</default>
         </entry>
-        <entry name="CriticalAlwaysOnTop" type="Bool">
-            <default>true</default>
-        </entry>
         <entry name="NormalAlwaysOnTop" type="Bool">
             <default>false</default>
         </entry>

libnotificationmanager/settings.cpp

@@ -347,20 +347,6 @@ bool Settings::dirty() const
     return d->dirty;
 }
 
-bool Settings::keepCriticalAlwaysOnTop() const
-{
-    return d->notificationSettings.criticalAlwaysOnTop();
-}
-
-void Settings::setKeepCriticalAlwaysOnTop(bool enable)
-{
-    if (this->keepCriticalAlwaysOnTop() == enable) {
-        return;
-    }
-    d->notificationSettings.setCriticalAlwaysOnTop(enable);
-    d->setDirty(true);
-}
-
 bool Settings::criticalPopupsInDoNotDisturbMode() const
 {
     return d->notificationSettings.criticalInDndMode();

libnotificationmanager/settings.h

@@ -51,10 +51,6 @@ class NOTIFICATIONMANAGER_EXPORT Settings : public QObject
      * Whether to show critical notification popups in do not disturb mode.
      */
     Q_PROPERTY(bool criticalPopupsInDoNotDisturbMode READ criticalPopupsInDoNotDisturbMode WRITE setCriticalPopupsInDoNotDisturbMode NOTIFY settingsChanged)
-    /**
-     * Whether to keep critical notifications always on top.
-     */
-    Q_PROPERTY(bool keepCriticalAlwaysOnTop READ keepCriticalAlwaysOnTop WRITE setKeepCriticalAlwaysOnTop NOTIFY settingsChanged)
     /**
      * Whether to keep normal notifications always on top.
      */
@@ -268,9 +264,6 @@ public:
     bool criticalPopupsInDoNotDisturbMode() const;
     void setCriticalPopupsInDoNotDisturbMode(bool enable);
 
-    bool keepCriticalAlwaysOnTop() const;
-    void setKeepCriticalAlwaysOnTop(bool enable);
-
     bool keepNormalAlwaysOnTop() const;
     void setKeepNormalAlwaysOnTop(bool enable);