Reverted the change to ValueTree::toXmlString(), as omitting the XML header could break existing code (will address this differently in a future commit)

modules/juce_data_structures/values/juce_ValueTree.cpp

@@ -1020,7 +1020,7 @@ String ValueTree::toXmlString() const
     std::unique_ptr<XmlElement> xml (createXml());
 
     if (xml != nullptr)
-        return xml->createDocument ({}, false, false);
+        return xml->createDocument ({});
 
     return {};
 }