Revert "trying heroku"

This reverts commit 98e9c99083

.gitlab-ci.yml

@@ -1,5 +1,4 @@
 stages:
-  - heroku
   - docs
 
 pages:
@@ -20,14 +19,3 @@ pages:
       - public
   only:
     - documentation
-
-staging:
-  stage: heroku
-  type: deploy
-  script:
-    - apt-get update -qy
-    - apt-get install -y ruby-dev
-    - gem install dpl
-    - dpl --provider=heroku --app=my_app --api-key=$HEROKU_API_KEY
-  only:
-    - master