Remove more remnants of print sequence message

I found this other place that was helping to display the message that warns that print sequcence is set per-object. Since the latter is no longer possible, this message shouldn't be displayed any more.

Contributes to issue CURA-458.

plugins/PerObjectSettingsTool/PerObjectSettingsTool.py

@@ -11,7 +11,7 @@ class PerObjectSettingsTool(Tool):
     def __init__(self):
         super().__init__()
 
-        self.setExposedProperties("Model", "SelectedIndex", "PrintSequence")
+        self.setExposedProperties("Model", "SelectedIndex")
 
     def event(self, event):
         return False
@@ -22,8 +22,4 @@ class PerObjectSettingsTool(Tool):
     def getSelectedIndex(self):
         selected_object_id = id(Selection.getSelectedObject(0))
         index = self.getModel().find("id", selected_object_id)
-        return index
-
-    def getPrintSequence(self):
-        settings = Application.getInstance().getMachineManager().getActiveProfile()
-        return settings.getSettingValue("print_sequence")
+        return index