range: Remove ::popup-menu emission

This signal is going away, and having context menus
on sliders is not really a thing anyway.

gtk/gtkrange.c

@@ -1883,16 +1883,6 @@ gtk_range_click_gesture_pressed (GtkGestureClick *gesture,
       mouse_location == priv->highlight_widget)
     mouse_location = priv->trough_widget;
 
-  if (mouse_location == priv->slider_widget &&
-      gdk_event_triggers_context_menu (event))
-    {
-      gboolean handled;
-
-      gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_CLAIMED);
-      g_signal_emit_by_name (widget, "popup-menu", &handled);
-      return;
-    }
-
   if (mouse_location == priv->slider_widget)
     {
       /* Shift-click in the slider = fine adjustment */