Merge branch 'delete-object-state-models' into 'master'

Delete object_state_models.md

See merge request gitlab-org/gitlab-ce!18588

doc/development/README.md

@@ -39,7 +39,6 @@ comments: false
 - [Sidekiq debugging](sidekiq_debugging.md)
 - [Gotchas](gotchas.md) to avoid
 - [Avoid modules with instance variables](module_with_instance_variables.md) if possible
-- [Issue and merge requests state models](object_state_models.md)
 - [How to dump production data to staging](db_dump.md)
 - [Working with the GitHub importer](github_importer.md)
 

doc/development/object_state_models.md

-# Object state models
-
-## Diagrams
-
-[GitLab object state models](https://drive.google.com/drive/u/3/folders/0B5tDlHAM4iZINmpvYlJXcDVqMGc)
-
----
-
-## Legend
-
-![legend](img/state-model-legend.png)
-
---- 
-
-## Issue
-
-[`app/models/issue.rb`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/issue.rb)
-![issue](img/state-model-issue.png)
-
---- 
-
-## Merge request
-
-[`app/models/merge_request.rb`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/merge_request.rb)
-![merge request](img/state-model-merge-request.png)
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