use package revert due to new warning log about using revert

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1894687 13f79535-47bb-0310-9956-ffa450edef68

poi-examples/src/main/java/org/apache/poi/examples/xssf/eventusermodel/XLSX2CSV.java

@@ -255,9 +255,12 @@ public class XLSX2CSV {
             minColumns = Integer.parseInt(args[1]);
 
         // The package open is instantaneous, as it should be.
-        try (OPCPackage p = OPCPackage.open(xlsxFile.getPath(), PackageAccess.READ)) {
+        OPCPackage p = OPCPackage.open(xlsxFile.getPath(), PackageAccess.READ)
+        try {
             XLSX2CSV xlsx2csv = new XLSX2CSV(p, System.out, minColumns);
             xlsx2csv.process();
+        } finally {
+            p.revert();
         }
     }
 }