Work around QHash::unite deprecation

Change-Id: Ibf199b5e3f2ca99b7e0cafe20893a509d9eab906
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qmljseditor/qmljssemantichighlighter.cpp

@@ -610,7 +610,7 @@ void SemanticHighlighter::reportMessagesInfo(const QVector<QTextLayout::FormatRa
     // but will use them only after a signal sent by that same thread, maybe we should transfer
     // them more explicitly
     m_extraFormats = formats;
-    m_extraFormats.unite(m_formats);
+    Utils::addToHash(&m_extraFormats, m_formats);
     m_diagnosticRanges = diagnosticRanges;
 }