fix subject line

Change-Id: I28ccbf825ed1535d4ccb640da01ce6ef778fde22
diff --git a/Jenkinsfile b/Jenkinsfile
index 8e3b9b4..172838f 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -93,7 +93,7 @@
         }
 
         mail to: env.recipients,
-            subject: 'Nightly bleeding edge ' + branch + ' released',
+            subject: 'Nightly bleeding edge ' + metadata['release_version'] + ' released',
             replyTo: 'cord-dev@opencord.org',
             body: '''Hi CORD Community,