ModelEditor: Make constants header self-contained

QT_TRANSLATE_NOOP was not defined

Change-Id: Iff31e1c16db9e648d65018a57c9e74cd5c0eb3aa
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/modeleditor/modeleditor_constants.h

@@ -25,6 +25,8 @@
 
 #pragma once
 
+#include <QtGlobal>
+
 namespace ModelEditor {
 namespace Constants {