Update Jenkinsfile

Jenkinsfile

@@ -5,7 +5,7 @@ node {
 
             sh"""
             kubectl port-forward svc/argocd-server -n argocd 8080:443&
-            sh 'argocd login 127.0.0.1:8080 --insecure --username $USERNAME --password $PASSWORD'            
+            argocd login 127.0.0.1:8080 --insecure --username ${USERNAME} --password ${PASSWORD}
             argocd app list
             """
             }