[github-339] compile issue in test

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1902790 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/test/java/org/apache/poi/xwpf/usermodel/TestXWPFParagraph.java

@@ -27,6 +27,7 @@ import java.io.IOException;
 import java.math.BigInteger;
 import java.util.List;
 
+import org.apache.poi.util.StringUtil;
 import org.apache.poi.xwpf.XWPFTestDataSamples;
 import org.junit.jupiter.api.Test;
 import org.openxmlformats.schemas.drawingml.x2006.picture.CTPicture;