QmlJS: Fix warning regarding forward declaration

Change-Id: I37dad31562565b75db2d92b2f956cf8ba629b5a0
Reviewed-by: hjk <hjk@qt.io>

src/libs/qmljs/qmljsimportdependencies.h

@@ -46,7 +46,7 @@ QT_END_NAMESPACE
 
 namespace QmlJS {
 class ImportInfo;
-class ViewerContext;
+struct ViewerContext;
 namespace Internal { class ImportDependenciesPrivate; }
 class ImportDependencies;