You need to add a route that maps to a controller action responsible for deleting an upload.
Since uploads seem to be associated with projects, you could nest the route under projects.
You already have a delete_upload method in your controller, so just ensure your route points to that.

config/routes.rb

resources :projects do
member do,
delete 'delete_upload/:upload_id', to: 'projects#delete_upload', as: 'delete_upload'
end
end