Slack integration posting once per stage instead of once per Deployment

GitLab CI/CD
1

I have a CI/CD pipeline set up with 2 stages in a repo at gitlab.com. I also have a slack integration set up that sends out a notification with Deployment checked and Notify only Broken Pipelines checked.

When the CI/CD pipeline runs, 2 identical notifications get sent to slack, once per each stage. I have this same setting on other projects and I only get 1 notification for the Deployment as expected.

Why am I getting 2 notifications for this project?

The .gitlab-ci.yml is below:

stages:
- deploy
- test

deploy:
  stage: deploy
  image: google/cloud-sdk:alpine
  environment:
    name: production
  script:
  - echo $SERVICE_ACCOUNT > /tmp/$CI_PIPELINE_ID.json
  - gcloud auth activate-service-account --key-file /tmp/$CI_PIPELINE_ID.json
  - gcloud --quiet --project $PROJECT_ID functions deploy gcf_function --entry-point defunction --runtime python37 --trigger-http

  after_script:
  - rm /tmp/$CI_PIPELINE_ID.json

test:
  stage: test
  image:
    name: postman/newman_alpine33
    entrypoint: [""]
  environment:
    name: production
  script:
  - newman run $POSTMAN_COLLECTION -e $POSTMAN_ENVIRONMENT