add extra setTitle method

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1901821 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/xddf/usermodel/chart/XDDFChartData.java

             this.valuesData = values;
         }
 
+        /**
+         * Set the Chart Series title.
+         * @param title chart series title
+         * @since POI 5.2.3
+         */
+        public void setTitle(String title) {
+            setTitle(title, null);
+        }
+
+        /**
+         * Set the Chart Series title.
+         * @param title chart series title
+         * @param titleRef cell reference
+         */
         public void setTitle(String title, CellReference titleRef) {
             if (titleRef == null) {
                 getSeriesText().setV(title);