JENKINS-31017: Description doesn't get the resolved variable

Chaning the description method to take the last occurance of given tags in the content
In this case user would be able to set the description with variables

src/main/java/org/jenkinsci/plugins/scripttrigger/AbstractTrigger.java

@@ -84,7 +84,11 @@ protected Action[] getScheduledActions(Node pollingNode, XTriggerLog log) {
     }
 
     private String extractDescription(String content) {
-        return StringUtils.substringBetween(content, "<description>", "</description>");
+        String [] des =  StringUtils.substringsBetween(content, "<description>", "</description>");
+        if (des != null && des.length >=1 ) {
+            return des[des.length - 1];
+        }
+        return null;
     }
 
     protected boolean requiresWorkspaceForPolling() {