Run multilingual audit stages on built-in Jenkins node

Jenkinsfile

@@ -100,6 +100,7 @@ pipeline {
             }
         }
         stage('Post-Deploy Multilingual Audit') {
+            agent { label 'built-in' }
             options {
                 timeout(time: 10, unit: 'MINUTES')
             }

Jenkinsfile.multilingual-nightly

@@ -1,7 +1,7 @@
 #!/usr/bin/env groovy
 
 pipeline {
-    agent { label 'external_pool' }
+    agent none
     triggers {
         cron('H 2 * * *')
     }
@@ -34,6 +34,7 @@ pipeline {
             }
         }
         stage('Nightly Multilingual Audit') {
+            agent { label 'built-in' }
             options {
                 timeout(time: 10, unit: 'MINUTES')
             }