NodeJS14 is no longer supported by Google Cloud Functions

In [nodejs cloudendpoints lab prepare_environment.sh](https://github.com/GoogleCloudPlatform/training-data-analyst/blob/master/courses/developingapps/v1.3/nodejs/cloudendpoints/start/prepare_environment.sh), you deploy nodejs14, which is no longer supported. If you update to the below, it will automatically choose the oldest supported version.
```bash
NODEJS_VERSION=$(gcloud functions runtimes list --region us-central1 --filter nodejs | head -n2 | awk ' { print $1 } ')
gcloud functions deploy process-feedback --gen2 --runtime $NODEJS_VERSION --region us-central1 --trigger-topic feedback --source ./function --stage-bucket $GCLOUD_BUCKET --entry-point subscribe --allow-unauthenticated
```
Also, google-p12-pem is no longer maintained, but I don't know which dependency is using it.