We list coffee-rails in bundler.d/assets.rb (https://github.com/theforeman/foreman/blob/e2dee7d6f7ffb505d317ca1b205f302ccd622063/bundler.d/assets.rb#L9-L10) with the following comment:

this one is a dependecy for x-editable-rails

But we dropped x-editable-rails in 623542da3c16d4033b94317e0ac757021132b884 (#29257) so we can probably get rid of it.