We need this in order to be able to add this migration for users that
use ActiveStorage during update their apps from Rails 5.2 to Rails 6.0.

Related to #33405

`rake app:update` should update active_storage

`rake app:update` should execute `rake active_storage:update`
if it is used in the app that is being updated.
It will add new active_storage's migrations to users' apps during update Rails.

Context https://github.com/rails/rails/pull/33405#discussion_r204239399

Also, see a related discussion in the Campfire:
https://3.basecamp.com/3076981/buckets/24956/chats/12416418@1236713081