The Refactoring
Now that everything has been refactored out of Kanban#find, there really is no use for it.  All that it does is to wrap the constructor so it’s now useless code.
Before
| 1 2 3 4 5 6 | # app/models/kanban.rb class Kanban def self.find Kanban.new end end | 
After
| 1 2 3 4 | # app/models/kanban.rb class Kanban # ... end | 
Review
After every refactoring session you will have some useless code left over. Sometimes it’s to keep a public API stable, sometimes it’s a simple delegate, and sometimes (like now) it’s just garbage that should be thrown away. Whenever possible, throw it away. If you need it back, git will be there.