Remove unused import from today's commits (#3159)

Author: dbmalkovsky

modules/flowable-dmn-xml-converter/src/main/java/org/flowable/dmn/xml/converter/DMNDIExport.java

@@ -18,7 +18,6 @@
 import javax.xml.stream.XMLStreamWriter;
 
 import org.apache.commons.lang3.StringUtils;
-import org.flowable.dmn.converter.util.DmnXMLUtil;
 import org.flowable.dmn.model.DmnDefinition;
 import org.flowable.dmn.model.DmnDiDiagram;
 import org.flowable.dmn.model.GraphicInfo;