Update timestamperWrapper.groovy

wrapper is not needed from 1.8+ version of pipeline

Author: aurelije

pipeline-examples/timestamper-wrapper/timestamperWrapper.groovy

@@ -1,7 +1,7 @@
 // This shows a simple build wrapper example, using the Timestamper plugin.
 node {
     // This is the current syntax for invoking a build wrapper, naming the class.
-    wrap([$class: 'TimestamperBuildWrapper']) {
+    timestamps {
         // Just some echoes to show the timestamps.
         stage "First echo"
         echo "Hey, look, I'm echoing with a timestamp!"
@@ -14,4 +14,4 @@ node {
         stage "Second echo"
         echo "Wonder what time it is now?"
     }
-}
+}