[Notifications] Remove unused selection clipboard handling

It is a remnant of when we still did the text selection code in
the popup on the QML side.

applets/notifications/notificationapplet.cpp

@@ -6,7 +6,6 @@
 
 #include "notificationapplet.h"
 
-#include <QClipboard>
 #include <QGuiApplication>
 #include <QQuickItem>
 #include <QQuickWindow>
@@ -84,13 +83,6 @@ QQuickItem *NotificationApplet::systemTrayRepresentation() const
     return c->property("_plasma_graphicObject").value<QQuickItem *>();
 }
 
-void NotificationApplet::setSelectionClipboardText(const QString &text)
-{
-    // FIXME KDeclarative Clipboard item uses QClipboard::Mode for "mode"
-    // which is an enum inaccessible from QML
-    QGuiApplication::clipboard()->setText(text, QClipboard::Selection);
-}
-
 bool NotificationApplet::isPrimaryScreen(const QRect &rect) const
 {
     QScreen *screen = QGuiApplication::primaryScreen();

applets/notifications/notificationapplet.h

@@ -31,8 +31,6 @@ public:
     QWindow *focussedPlasmaDialog() const;
     QQuickItem *systemTrayRepresentation() const;
 
-    Q_INVOKABLE void setSelectionClipboardText(const QString &text);
-
     Q_INVOKABLE bool isPrimaryScreen(const QRect &rect) const;
 
     Q_INVOKABLE void forceActivateWindow(QWindow *window);