QMakeNodes: OBJECTIVE_HEADERS doesn't exist

Change-Id: I788c018bfc8bb608ea82696618d4eb9e0d2fe918
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

src/plugins/qmakeprojectmanager/qmakenodes.cpp

@@ -1244,7 +1244,6 @@ QStringList QmakePriFileNode::varNames(ProjectExplorer::FileType type, QtSupport
     switch (type) {
     case ProjectExplorer::HeaderType:
         vars << QLatin1String("HEADERS");
-        vars << QLatin1String("OBJECTIVE_HEADERS");
         vars << QLatin1String("PRECOMPILED_HEADER");
         break;
     case ProjectExplorer::SourceType: {