You can solve it much easier with configMap and then mount the configMap as a volume which will be resolved in a file.

Below is example how to proceed with it (Note! You will need to use a proper image for it as well as some other changes how mongo shell works):

1. Create a configMap from file. Can be done by running this command:

   $ kubectl create cm mongoscript-cm --from-file=mongoscript.js
   configmap/mongoscript-cm created
   

   You can check that you file is stored inside by running:

   $ kubectl describe cm mongoscript-cm
   

2. Create a job with volume mount from configmap (spec template is the same as it used in pods):

   apiVersion: batch/v1
   kind: Job
   metadata:
     name: mongojob
   spec:
     template:
       spec:
         containers:
         - name: mongojob
           image: ubuntu # for testing purposes, you need to use appropriate one
           command: ['bin/bash', '-c', 'echo STARTED ; cat /opt/mongoscript.js ; sleep 120 ; echo FINISHED'] # same for command, that's for demo purposes
           volumeMounts:
           - name: mongoscript
             mountPath: /opt # where to mount the file
         volumes:
         - name: mongoscript
           configMap:
             name: mongoscript-cm # reference to previously created configmap
         restartPolicy: OnFailure # required for jobs
   

3. Checking how it looks inside the pod

   Connect to the pod:

   $ kubectl exec -it mongojob--1-8w4ml -- /bin/bash
   

   Check file is presented:

   # ls /opt
   mongoscript.js
   

   Check its content:

   # cat /opt/mongoscript.js 
   var operations = [];
   db.product.find().forEach(function(doc) {
       var documentLink = doc.documentLink; 
       var operation = { updateMany :{ 
   "filter" : {"_id" : doc._id},
   "update" : {$set {"documentLinkMap.en":documentLink,"documentLinkMap.de":""},
       $unset: {documentLink:"","descriptionMap.tr":"","news.tr":"","descriptionInternal.tr":"","salesDescription.tr":"","salesInternal.tr":"","deliveryDescription.tr":"","deliveryInternal.tr":"","productRoadMapDescription.tr":"","productRoadMapInternal.tr":"","technicalsAndIntegration.tr":"","technicalsAndIntegrationInternal.tr":"","versions.$[].descriptionMap.tr":"","versions.$[].releaseNoteMap.tr":"","versions.$[].artifacts.$[].descriptionMap.tr":"","versions.$[].artifacts.$[].artifactNotes.tr":""}}}};
       operations.push(operation); 
   });
   operations.push( {
       ordered: true,      
       writeConcern: { w: "majority", wtimeout: 5000 } 
   });
   db.product.bulkWrite(operations);